Refitting Your Imperial's Air Conditioning System To Newer Refrigerants


Imperial Home Page -> Repair -> Air Conditioning -> Converting To Newer Refrigerants

Tips from Ron:

It must be that time of year again, I swore I was going to stay out of this but those darn hairs on the back of my neck!

I would like to understand where you came up with $200 for labor. For that retrofit labor, I have a lot of sub work I could send to that shop! I added up the non overlapping FLAT RATE hours for the above work and without any time allowed toward diagnostics, or evacuation and recharge the FLAT RATE HOURS comes to 4.8 Hours, that means your model shop has a FLAT HOURLY RATE of $41.67/hour, where in this country is there such a low overhead shop with competent techs? When I add in the usual 1 hour diagnostics, and another 1/2 hr (optimistic) to dial in a "never before had R134a system", that comes to 6.3 Hours which equals a shop charging $37.75/Hour.

I know - what's my point?

SOME OF MY points are:

NO TWO SYSTEMS ARE THE SAME, or have the same problem, or will convert exactly the same, or will COST the same --- period. SOME SYSTEMS CONVERT BETTER THAN OTHERS SOME SYSTEMS ARE NOT CONVERTIBLE, with/without MAJOR EXPENSE. MOST SHOPS LIKE TO PAY THEIR BILLS and their EMPLOYEES like to take home a LIVABLE PAY CHECK, and around here that means A FLAT RATE of about $65/hour for a non-dealer shop. I haven't found a way to "gold plate" my pockets doing A/C conversions, the truth is that most "classic cars" we CONVERT are among our LEAST PROFITABLE BLANKET STATEMENTS and inaccurate examples only add to the confusion, and after 5 years of conversions, I still get an education on most systems that I do.

Additional comments from Dick:

Just to support Ron's statement (and trying NOT to add any fuel to the discussion), but after 50 years of working on old cars, doing it as my own profit-making (Hah!) business for a 15 year part of that time, I can honestly say that nearly every car presented something I had not seen before, and consequently taught me something new and worthwhile. Regardless of the shop labor rate, I always wound up donating much of my time at no cost to the customer sorting out the weird problems we got presented with.

I learned the hard way never to make a blanket statement about what something was going to cost or take in the way of parts or time.

One way to run a business doing that is to overestimate the potential cost (which scares away some customers) and then overcharge the ones that bite to make up for the really bad baths you inevitably take. This is the well known national chain's approach to transmission repair. Not an example one wants to follow.

Additions from Joe:

The price of $200 comes from Jack Crowley at C&J in Berwyn, Pennsylvania -- a suburb of Philadelphia. Jack operates on volume and keeps his pricing accordingly low. What I would recommend is to give him a call at 610-647-6072.

Jack is a nice guy, and will take the time to explain his pricing structure.

To date Jack has performed over 300 conversions - his Mercedes being the first to get the conversion.

I have sent one of the guys in my LCCI club to have his Bimmer converted - the cost to Tom was $200.

Please let me know if you have any more questions. As a matter of fact, if you have questions not answered by the article, or have further questions, please give Jack a call yourself and assuage your curiosity. You obviously live in a different part of the country than he does and he won't be able to profit from you. Jack will give you and honest appraisal of what is involved in a R134a conversion.

Excellent Tips from Tony Dickson:

Both R406A and GHG-X4 (now called "Autofrost", "Chill-it," and other names) are 100 percent legal for use in cars. 

As far as using a modern R134a refrigerant (like in a 1995 Neon) with a new dryer, compressor, hoses, etc. here is my experience:  You're looking at replacing some components either way, but the switch to R406A is going to require MUCH less expense, MANY fewer new parts, and will yield MUCH better performance and efficiency than R134a.   Basically, DO NOT(!) convert your R12 car to R134a or any of the R134a-based refrigerants (FRIGC comes to mind). They are far less efficient than R12 and R406A, GHG-X4, etc. Also, they are HIGHLY incompatible with R12-type oil. They operate at radically different pressures, so calibration of R12 expansion valves won't be optimal. Also, since 134a is so inefficient, one must use larger compressors, condensers, and evaporators to get the same level of cooling as from an R12 system.  This is difficult and expensive to do on an existing system, so you get much less cooling with 134a.  To convert to 134a PROPERLY so as not to shell any of the components, you're going to need: 

a)  All new hoses (The R12 hoses are permeable to the smaller R134a molecule) 

b)  All new seals and O-rings (ditto above) 

c)  A rebuild of your V2/RV2 compressor (because this compressor design uses an oil sump and pump which cannot be "flushed" of oil like other non-sump type designs, and because 134a is so violently incompatible with 12-type oil, you have to get ALL of the old oil out.) 

d)  New receiver-dryer with XH7 or XH9 desiccant 

e)  And you should really purchase a parallel-flow condenser to try and make the system work at least marginally, if not optimally well. 

Now let's compare that to using R406a or GHG-X4: 

They are MORE efficient than 12, yet it operates at similar pressures, so the expansion valve calibration will remain optimal and your existing condenser and evaporator will function MORE than adequately. 

They are completely compatible with R12 type oil, so no system flush or expensive compressor rebuild. 

You still need new hoses, because R12 type hoses are permeable to the smaller R406a factions' molecules. 

Ditto new seals. (New hose-to-hose and component-to-component seals, you don't have to mess with any compressor or other internal seals). 

The choice is crystal clear here, isn't it?  Now I have to ask YOU a question: Why are you converting to anything?   R12 is still around, you know, and anyone who tells you otherwise is lying or ill-informed. There is plenty of it in the US. There is MORE than plenty of it in the US.  Some garages will tell you that R134a is the only legal refrigerant.  That's wrong. Some will tell you that 134a "moves more heat" than R12.  That's also wrong. Some will tell you that no flush, rebuild, or anything else is needed when converting to 134a. That's dangerously wrong. Either use 12, or use 406a, or use GHG-X4.

Tips from Jeff:

Now that Air Conditioning Time is here, we factory reps start getting a lot of questions from people with older cars. So I thought it might be helpful to share with the group the latest thoughts from the good people at General Motors.

I will begin with the disclaimers that I am not a certified technician, and am not telling you to try any of these steps on your cars, and that what is below is a summary of published information that is available in Service bulletin form from General Motors. This is merely an attempt to raise awareness of the differences between R-12 and R-134a based systems. Hopefully it will be of use to y'all. These are professionals on a closed course. Do not try this at home.

As you know, all modern cars utilize the R-134a coolant. This coolant is supposed to be inert, and therefore ozone friendly. For those of us like me who are not convinced that freon is the problem (and marvel at how the damage to the ozone layer looks like the major jet aircraft flight patterns), we wonder what they will find wrong with this one.

The secret of R-134a, as i like to tell, is that it won't hurt the environment, but it won't cool it, either. R-134a is not as efficient as good old R-12. To get performance similar to an R-12 system, a modern car has a larger evaporator core, And the system runs at a higher head pressure than a comparable R-12 system. Furthermore, the refrigerant oil for an R-134a system is not compatible with the refrigerant oil of an R-12 system. And the inlet fittings (both high and low pressure) are not the same.

Translating back into English, this has several ramifications converting our older cars. First, it will not be too difficult to adapt R-134a to a car from about 1988 or newer. the system will have to be vacuum evacuated, the fittings adapted, the new R134a and refrigerant oil added, and charged. Then the system will not work as well as it did.

Kits are available through dealers (we're not the only ones who have them) and this newer car can be converted for about $200, plus or minus.

For the older cars, hopefully one can begin to see the magnitude of the situation.

First, the system must be completely vacuum evacuated. Then, the hoses must be replaced to withstand the higher pressure of the new system.

Marginal fittings will blow out. The existing compressor may or may not be able to handle the higher pressure, it may have to be changed. And finally, the inlet fittings (high and low pressure) must be changed. And after all that is accomplished, it will not be as sold as it was new- R134a is not as efficient.

I am just outlining a situation, not telling anyone what to do. On my personal vehicles, they will remain on R-12 as long as it is available, which should be into the next century. There has been another coolant which is being experimented with, I believe it contains propane. With all of the older cars out there who manage to leak freon, I personally would not like to have all of them leaking propane. Cigarette, anyone?

Finally. I am very suspicious of Miracle Replacements for R-12. If there were a miracle replacement for R-12, I sincerely believe we would be using here at General Motors.

Tips from Bob:

If you are a Do-It-Yourself AC mechanic, there are many substitute refrigerants for your car, some of them are dangerous, but still legal. You can browse all the stories about these refrigerants on the Web, you can legally create your own refrigerant and use it, but I think there is a better way.

Read the April 97 issue of MOTOR Magazine, it will distill the topic down to a reasonable decision for you to make. For example, if you own a 79, or later, Chrysler with the Nippondenso C-171 compressor, you'll learn that with R-134a you'll need to replace that compressor; also, they list seven or eight others that won't tolerate the higher pressures that R-134a imposes on the system. The older V-2 may not work either, the front shaft seals aren't designed for the higher pressures of R-134a.

There is one, new refrigerant that is EPA approved and available called FR-12, also FRIGIC - concocted by Intermagnetics General Corp and now nationally distributed by Pennzoil, out of Houston. The changes you would need to make are minimal, the cost is much less than R-12, and, most important, the physical and chemical properties are quite close to the R-12 unit you already have.

There'll be no high pressure seal blow-outs, the hoses and fittings and O-Rings are compatible. Many bad stories are circulating about this refrigerant because it does not offer a large profit job for the trade mechanics - it simply doesn't take a pile of money to make your car cool again. If your hoses or expansion valve are leaking, if the compressor is noisy, then no kind of refrig is going to cure those problems, fix them also.

You can call 1-800-555-1442, Intercool Corp., and get an idea of where you might take you car in your location. This subject is rapidly turning into a gigantic mess, read the magazine before you commit to any retrofit.

Question from Larry:

I have a question for the people who know Air Conditioning. I found a kit to convert the old R12 systems to 134-A type refrigerant. When I had my Bronco II converted the man said he had to change the condenser and all the seals. ($256.00)

Was he right and was the price right? Or can I convert my 1982 Imperial with a kit for $33.00??? Something doesn't sound right? The R12 is a little low I can see some bubbles some of the time, and it is clear part of the time?


From Steve:

You can do it that way but its not the best in the world. Ideally the system should be flushed, dryer changed and all new o-rings. Hoses can also be replaced but they don't leak as much as was initially thought because the oil seals them up.

If your system is only a little low you will be much happier just having the system topped off with R12.

From Dick:

If you have only a minor leak in the R12 system, perhaps you only need a few ounces of R12 to top it up, and in that case I would certainly stay with the R12.

If your system is leaking and you don't want to go to the expense of finding the leak, yes, you can use the $34 kit to change it over. No, you don't need to do all the other stuff. This will cause a storm of argument from others on the IML, but I will turn off my hearing aid. I have done this to 5 cars now, using the $34 kit, and they all cool just fine, thank you.

The guy who did all the expensive stuff did a good thing for you, because money and you take your chances. You get what you pay for, but the El-cheapo kits do work just fine.

From Elijah:

Unlike Dick, I can't turn off my hearing aid (isn't that convenient!!!), but I CAN enjoy 38-40 degree air blowing from the A/C vents in my '71 Imperial, courtesy of the el-cheapo $34 R-134a kit that I used on the car in 1999. The car has the original compressor, hoses, condensor, and evaporator -- the only thing that has been changed is the expansion valve.

The system has a small leak that I've just never bothered to track down. I do have to put in 2 to 3 cans a year, but at a cost of less than $2.50 a can, who cares?

The system works great here in the Chattanooga, TN, area, which can be pretty darn hot and muggy in the
summer. And the car is midnight blue with a black vinyl top, so it's just one big ol' heat sink when the sun is shining.

I figure that five years is a pretty good test run, and the system is still working great. As always, your mileage may vary.

From Paul:

This is a no brainer. My '65 Imperial still has its old original leaky system. If I can make it work again with R134a instead of having it recharged with R12 (like I have twice before) at $175.00 per pound, or paying over $1,000 to convert it, I'm going for it. Like you say, who cares if it takes a pound or two every so often at $2.50 per pound?

I saw a kit like this advertised in my most recent J.C. Whitney catalog. If it doesn't work, I have only lost the price of a tank of gas.

Question from Bob:

Looking for words of advise on converting a '62 A/C system to R-134. Anyone with EXPERIENCE and words or caution or pitfalls they've run into would be helpful on this. R-12 is just getting too hard to find anymore, (not to mention outrageously expensive), and sooner or later will be totally unavailable anyway. So I would appreciate anything that anyone has to offer on this topic...


From Jim:

I use Freeze 12 in my '73 with no problems.

From Don:

My $0.02 worth: A friend of mine works at an A/C shop in Southern California. Used to charge $800.00-1300.00 for a complete conversion to R-134- new hoses, seals, oil, rec/dryer/expansion valve etc. Then somebody in the shop went cheap on their personal car-rec/dryer, expansion valve, oil and charging system with R-134 at 80% of factory R-12 specs. Worked fine! Owner started doing same conversion on all cars, charged a lot less and still made a fistful of money and had fewer comebacks than with full conversion.  Planning to do the same on my '66 Crown.

Question from Patrick:

I have decided to go over my A/C system before it gets a million degrees here. I have had the car for 2-3 years with no A/C. I have taken all the related hoses in and have had new ones made. I have a new compressor I purchased last year ready to be installed.

I have made the decision to go with the old R-12 since the car designed for that, my concern isn't about the cost but more with what the system was designed for.

The parts counter jerk at my parts store claims I should also replace the drier and clean out the rest of the components before filling the system.

Do I really need to purchase another drier?

Since I have the system apart, is there any way I can clean it out on my own?


From Matt:

Yes, I would do it right, put the new drier on.

From Dick:

He's not a jerk, he is trying to save you a lot of grief. Of course no oneknows what has accumulated in your system while it was open, but it is almost certain your drier is contaminated. They are cheap and easy to change.

If you want a trouble-free job, take it to a pro and have the system flushed, and a new drier installed. It will be really disappointing if a particle of crud gets in your evap valve and shuts down your cooling after a week of use! It will be even more disturbing if something circulates around and causes your compressor to have a fit! I like to leave a system on the vacuum pump at least overnight, too, before charging it, just to see if there is any moisture in the system (turn off the pump and watch the manifold gauge - it should hold at -30 inches of mercury for at least overnight - if it doesn't, you'll be wasting your money to put refrigerant in the system without fixing it.)

From Phil:

By all means, replace the filter/dryer. The new compressor warranty probably requires flushing the system, too.

I bought an a/c flush kit from JC Whitney-it worked just fine but it's quite messy...don't even think about flushing the system indoors.
Once the compressor and filter/dryer are removed, it's easy to flush the evaporator and condenser from the compressor fittings.

My first attempt left some flush in the system (I didn't blow enough compressed air through the system to remove all the flush due to ignorance and being overwhelmed by the mess) and I couldn't get any suction from the compressor. I removed the hoses and filter dryer and repeated the process with compressed air until only dry air discharged from the system.

After reassembly, and a lengthy run with the vacuum pump, the system works great. I should mention that this was a lesser Mopar...a K-car, in fact, but the procedure is the same.

A few final thoughts: your new compressor's crankcase should be full of oil. Make sure the quantity of oil in the compressor is equal to the total oil required by the system since you will have removed all residual oil. Consider replacing the two schrader valves and the expansion valve. R-12 is expensive and your system probably requires about four's a gamble putting that much R-12 in an antique system. It might be a good idea to put a minimal charge on the system, close the gauges, and check for leaks with a "sniffer"...or at least let the system set overnight to see if it holds pressure.

From Steve:

The parts counter person is correct. The drier should be replaced any time the system is opened. Don't install the new drier until you are ready to vacuum and charge the system.

From Henry:

I have just done three old car AC's. All are working very well and will almost give you frost bite if you turn them on Max Air high.

Here are the tips I can give:

1. New filter/dryer -- A must. Old one is probably contaminated.

2. Replace all 'O' rings with green ones and the two gaskets on the compressor.

3. Use air pressure to blow out the condenser and hoses.

4. If you can, put a vacuum on the system to be sure it does not leak. If you have good hoses and have done steps 1 and 2 correctly, it should not, unless the condenser or the evaporator have holes in them. I did not have a vacuum pump, so I skipped this step.

5. Use a 134a conversion kit, about $30, to charge the system. R12 is expensive, and the Mexican stuff is often low quality. I have not noticed any decrease in cooling capacity or rate with R134a. There are excellent lubricants and leak sealants in the 134a included with the kit, and they mix with the oil already in the system.

From my experience, using R12 is a waste of money if cooling your car is what you are after. Authenticity is another matter, but since the car is a driver, I would expect your desire would be to get the cheapest cool air you can.

From Chris:

If anyone is contemplating a switch from R-12 to R-134 in a 1961 or later Mopar, I've had very good results doing the following:

1. Change oil in compressor. I had a new one with the correct oil already in it, so this process was not

2. Have system flushed of old oil and contaminents.

3. Remove EPR valve from back of compressor. This valve works a little too well with R-134 when the temps get high, restricting cooling ability.

4. Since there is no longer an EPR valve to prevent evaporator icing, a thermostatic switch should be installed that cuts off the compressor when things get too cold. Then cuts it back on when the threat of icing passes. Yes, R-134 will cool so well that icing is an issue.

5. R-134 typically works at pressures above R-12, so it would be a good idea to install a safety cut-off switch on the high side.

6. Optional: An auxiliary fan in front of the radiator will help to lower condensor pressure and temp for better performance in stop-and-go traffic. The fan can be manually operated, or be wired to operate when compressor is running.

Note: With the externally-mounted by-pass (EPR) valve in 1960 and earlier compressors, I have found that they do not work particulary well with R-134. Apparently these extarnal valves don't allow correct pressures to be maintained with R-134. And since these valves can't be easily removed, a switch to a later RV2 compressor would be necessary to get good results from R-134. (Bolts right on to existing brackets, but later hose connections would also be needed.) Or stick with R-12.

From Ken:

The nice thing about upgrading or modifying "drivers" is it leaves more N.O.S. and good used original stuff for serious restorations.

Radial tires are certainly an improvement over bias ply tires and I use them on my vintage vehicles. I have heard stories of some old style narrow rims distorting from the use of radials, but I have never seen that happen.

I believe virtually any engine that originally used straight weight oil can use multi grade. At least those produced since the 1940s.

There are a couple of problems, however, when using R-134a in some A/C systems designed for R-12.

(A bit of "tongue-in-cheek" warning for some of the content below.)

The heat transfer properties of R-134a and R-12 differ. R-134a usually needs a much larger condenser, smaller duct tubing and perhaps a higher velocity blower fan to keep the temperaure at the interior vents comparable to the original R-12 system.

R-134a needs "barrier" hoses under the hood and, all other things equal, has a higher working pressure.

In the extreme heat of the desert southwest, a large fixed blade non-clutch fan or supplimental electric cooler fan may be needed if you drive in heavy daytime traffic.

There is a company in Florida that converts original R12 systems to R-134a, but I have also heard some R-12 systems work just fine with R-134a. I do know of a couple instances where original R-12 underhood hoses ruptured when the system was changed to R-134a and the original hoses were retained.

Point is, I'd do some research before simply adding R-134a to an R-12 system or using one of those forty dollar "conversion kits."

We "desert rats" take our A/C as seriously as any snow belt resident does his/her heater/defroster! ;-)

Question from Greg:

I've read with increasing interest all the posts regarding converting our air conditioning systems to R134a. I'll admit there have been some mighty good arguments in favor of the switch. I am about ready to 'fire up' my ac system as my restoration has reached that point. All the hoses have been replaced with the 'newer style' in preparation for the conversion. Now, my business neighbor who owns an auto repair shop has raised a question in my mind as to the necessity of such a change. He showed me a can of Freeze 12 which he claims is 'ozone friendly' and far less expensive than R12. He also added that in the DEEP south (Mobile, AL) it is difficult to get air at the registers much lower than 48-50 degrees with 134a. With the Freeze 12, he claims air temps (again this is in a very hot, muggy climate) around 38-42 degrees! It is so sweltering here in the summertime, I certainly want the 'conditioned' air at the registers to be as cold as it possibly can!

IF the ozone issues have been resolved and the product is not horribly expensive, my question is should I continue with my plans to convert my system or go with this 'new' product and keep my system factory. Any facts, statistics or even opinions regarding Freeze 12 would be greatly appreciated. BTW, if all goes as planned, the Imperial's rebuilt engine will be started on a dynamometer (at the machine shop where it was rebuilt) for the first time this week! I am eagerly awaiting the chance to turn the key and hear that engine roar!


From Kerry:

I would not put R12 in anything unless it was just a touch up on a functioning system.

From Bob:

FR-12, originally formulated by Magnetic General, a MA company several years ago as a super cleaning agent is available at very low prices and an excellent replacement for R-12, whose quality is in doubt because of importation from China and elsewhere and which is cost prohibitive.

FR-12 will easily replace R-12 : Is compatible with original oil, but a small amount, one ounce, of PAG Oil is suggested. Will not harm seals or gaskets. Does not require replacement of any mechanical, electrical devices, or hoses. Runs and cools without changing anything related to the compressor. Runs at LOWER high side pressures for equal or lower cooling temperatures. Runs with slightly less refrigerant than the an R-12 system. An R-12 gauge set will work fine. License is req'd by US Government. The Chrysler Expansion valves have a disc on the underside of the valve than can be adjusted to increase or decrease cooling; slight movements of the cap will do this. (this valve should be examined regardless, at the time work is done; it's seal is prone to leak). A normal charge of FR-12 will not result in a sight glass free of bubbles; not to worry, the correct amount is only slightly less than R-12 and ignore the sight glass; do not overfill. Other substitutes are not chemically compatible with the contents of various parts of the system; too much data here to be specific. R-134 has pressures that are opposite FR-12 or R-12 performance pressures. Remember the original factory complaints with it in brand new cars - the condensers were too small, pressures too high, and no cooling. The new Chrysler LH cars were well thought-out in this area - no problems. Some conversions with R-134 were prone to problems.

From Steve:

We have been using Freeze 12 in our shop for the last two years, in fact I have some in my 71 Imp. It has worked very well and we've been able to get great outlet temperatures with it. It's true that you won't be able to get as cool with the 134 especially in a larger area such as the interior of an Imperial.

As far as I'm concerned there isn't any drawbacks to Freeze 12, at least we haven't encountered any. I know there is some real junk out there on the market and I'm sure there is probably some stuff that is flammable and can contaminate your AC equipment. We've had cars in our shop that have had up to 3 different types of freon in their systems.

From Paul:

I have had a couple of my regular driver cars converted from R-12 to 134A. I did it when the system required repair, and have not been disappointed. One of the cars is an '86 Lincoln Town Car that I have stored in Arizona and use for 10 days every 6 months. The system has been reliable, and cools the car down as well as anything I have ever used.

Someone here has already said that they would only use R-12 as touch on a functioning system, and I would agree with that. One of the cars that I had converted was still full of R-12, and I received a credit from the shop for 4 lbs which paid for part of the work on my car and all of the 134A.

I have not done any of this work on my Imperials since none of them are driven often enough to keep the systems operational.

Question from Philippe:

What should be the filling charge with R134 if my '57 FSM says 3 pounds (of R12) ?  I've charge the system with 134 (yes, I've changed the oil with lots of  problems: I needed to remove the V2 compressor oil sump and had a lot of leaks with a "homemade" gasket. Bought one new from Collector Auto Supply and I have no leaks now .. I've also put correct fittings and a new drier). I've put around 2 1/4 pounds and the system works but the air is not very cold, just refreshed.   Any ideas about this?

Reply from Dick:

The amount of R134 you put in there sounds about right if the original R12 was only 3 pounds. Verify that is the correct amount, though, because it sounds very low to me. See if there is a metal tag on the compressor which tells you how much R12 was supposed to be in there - I remember more like 4 or even 4.5 pounds for those old systems.

Your system should have a sight glass - if it does, see if it is running clear, or if you see suds going past the window - if you do, you could probably safely charge it a little higher. Watch those pressures, though, don't exceed 275 PSI on the high side, hot day, system running at maximum cooling.

Question from Simo :

I wonder if somebody does have exact information about changing the old R12 Air Condition system to work with the new refrigerants?

Does there exist some hardware which have to be changed in older cars?

The new refrigerant should be R 134A or ?

I have heard that there is an other refrigerant called as R 406A and this should function well with the originally for R12 planned systems. Ever heard about R 406A?

Does somebody have experience with R 134A or R 406A?

Does it make difference if the car comes from the sixties or nineties with the R12 system?



From Manuel:

Well, I am certified to handle refrigerants and I will tell you what I know...

Under current law, new automobiles must use R134A or R22. No hardware needs to be changed to convert to either of the above, but I am unsure if you must change the oil in the system - I think you have to. I will find out for sure if you want. I am not sure because I usually work with restaurant equipment that uses R12, R502, and R409A. Changing the oil in a system certainly falls in the category of "not fun". :) 

> I have heard that there is an other refrigerant called as R 406A and this should function well with the >originally for R12 planned systems. Ever heard about R 406A?

I think you mean R409A (at least that's what it's called in the US), which is the current replacement for R12. This is an excellent refrigerant that actually out-performs R12 (You use less and it gets colder). R409A has the advantage that you do not need to change the oil when converting from R12 - You just evacuate the system with a vacuum pump or let the A/C compressor do it for you then you charge the empty system with R409A.

The problem is that it is not technically legal to put R409A in automobile A/C systems in the United States right now. The main reason I know of is that they want to limit the refrigerants used by the people who service the vehicles (less chance for error), but this doesn't make any sense to me. Europe has been using R409A in motor vehicles for years now with no problems and it is thought it will eventually be legal here in the US too.

The bottom line is that R409A works great in automobiles, but you're not supposed to do it. My Ford Aerostar van I drive has been on R409A for a year now and it works great!! 

> Does it make difference if the car comes from the sixties or nineties with the R12 system?

Not if you're using R409A and I don't think it makes a difference on the other systems either.

You more than likely DO need to change compressor oil when changing from R12 to R134a. Most R12 systems (especially older systems) used mineral oil. R134a must use polyol ester oil. If newer R12 systems used a different oil, it should state what type on the compressor - if not assume the compressor has mineral oil.

The maximum recommended amount of mineral oil that can be present in a R134a system is 5 percent. 

From Frank:

The drier element is usually a ceramic, since it takes abuse better and it less likely to migrate through the system. You can still get generic replacement filter/driers for these cars since the fitting are all similar. However, the new ones are physically smaller. Functionally this does not matter. Could be a problem if you "show" the car.

You can recondition you elements by heating to about 250-300 degrees F for a few hours, but I have not ever done so. I have done quite a bit of auto a/c work and have a few rules that have always worked for me:

1) Keep everything CLEAN

2) Use a new filter/drier EVERY time you open the system.

3) Use NEW gaskets/O rings on every connection.

4) Use a light coating of refrigeration oil on all gaskets and O rings.

5) Pull a good, long vacuum on the system before recharging. (The A/C system in my 83 Imperial had quite a bit of internal corrosion since the factory skimped on this!)

6) Weigh carefully. Every system has a tag that states the amount (ounces is weight, not liquid volume) of charge to add.

7) When in doubt, a slightly UNDER charged system is better than one that is over charged.

Finally, just because you found no leaks under vacuum, does not mean that you will not find any when you pressurize the system. Leaks are funny things.

From Dave:

Your old Mopars will work fine with the new refrigerant (R-134A), but you may want to make sure that all of your hoses and seals are in good shape. And if your clutch is iffy, you'll need a new one. Also, I'm not familiar with air conditioned Darts, so I can't speak for the condensers in them.

The larger MoPars had HUGE condensers in them, which work fine, but your Dart probably has a much smaller one (due to the narrow front clip) so you might have to upgrade the condenser. The head (discharge) pressure with the new refrigerant will be a little higher under very warm conditions. DO NOT put the synthetic PAG lube oil in the system, since this will eat the seals. Just flush the system thoroughly, and re-fill the compressor with the original mineral oil, with a couple of ounces extra. (The new refrigerant does not carry the oil around as well as R-12 did) My last job was as a system test technician for automotive air conditioning systems, and the R-134A was actually more efficient than R-12, but with slightly higher pressures. 

You do NOT need to go to the polyol ester or polyalkylide glycol oils to use the R-134A. It will eat the seals in your system unless you can find the proper seal materials (including the gaskets in the compressor and the tiny seals in the TXV) in the proper sizes for the RV-2 compressor. Another very nasty side effect of these oils is that they EAT paint and cause very rapid oxidation of unprotected steel parts! The mineral oil will work fine if you simply add a couple of ounces extra to the system. Our lab did EXTENSIVE testing of lubricants, and found that the PAG oil also did not lubricate worth a hoot. 

From Mark:

The filter/drier in the A/C system is the canister with the sight glass in it. It is in the system to remove moisture and dirt from the refrigerant in the system. Any time that the A/C system is opened up the part that is removed and the system must be capped to prevent moisture and dirt from getting into the system. On our Imperial the filter/drier are hard to find and costly. What I have done is to remove the filter/drier and place it in my oven on low heat for a few hours uncapped to remove the moisture from the silicone gel . Cap it right away when you remove it from the oven the silicone gel acts like a sponge and will start drawing moisture form the air.

Another place to check on dirt in the system is to remove the Thermostatic expansion valve the tube that enters the valve will most likely have a screen filter in it, and sometimes the dirt can add a restriction to the flow of refrigerant in the system The refrigerant oil that is used in the system is a special oil and should have a viscosity of 500 SUNISO 5GS is the one that I use. Never use a motor oil in a A/C system.

Question from Tom:

I have heard conflicting reports on whether the v-twin compressors can handle the new refrigerants. If they can should I do a rebuild on the one I have or just slap it back in? It didn't appear to have any leaks when I took it out.


From Steve:

It has been my experience that your stock compressor will do fine with 134a. Those a/c systems were massively over designed to be able to run the dual air option in the hottest of weather. My ’73 would freeze you out of the car with 134a and dual air although if the car was really hot it took a while to start cooling good. I imagine with a single air system you would not have the “lag” time like I had with the dual system.

Usually the front shaft seal is what fails on the compressor with age. Since you already have yours off I would have it rebuilt or replace it with a rebuilt. If it was still on the car I would probably chance it, but since yours is off and if you factor in the cost of the dryer and refrigerant etc it would probably be a good investment to have the compressor rebuilt.

From William:

When the whole R-134a situation was on the horizon and the upgrading to it was being discussed, I consulted with a friend of mine (an ex-Chrysler parts man) that worked for an a/c parts manufacturer. He said that the Chrysler RV-2 compressor (and I suspect the earlier RV compressor it evolved from, plus the other compressors used by the main stream American manufacturers in the middle '60s or so) were plenty stout to handle the added pressures of the new refrigerant. No need to change them for some of the newer Sankyo or similar compressors.

I concur that most everybody's factory a/c system on the bigger passenger vehicles, from about '65 on, were designed with enough capacity to keep everything nice and frosty in the hottest southwestern USA weather. I recall that one maker designed their systems to handle a 110 degree F day in Phoenix, sitting idling in traffic.

Although the compressor designs did improve, the key to the added cooling capacity was the huge condensors (with more fin/inch than the earlier models) they were using. If you look at some of the later '50s condensors, they don't have nearly as many fins/inch and resultant heat exchanging capacity as the mid-'60s condensors did.

One thing that has been noted about R134a conversions is that there is sufficient air flow across the condensor at low speeds. If the pressures go higher than normal, just like the R-12 systems, cooling performance deteriorates until sufficient air flow is restored (by vehicle forward movement or an extra electric fan kicking on).

In about '73 time frame, Chrysler issued a service bulletin regarding a/c performance. In certain conditions, it was possible for the hot underhood air to "recycle" and go back through the condensor and radiator. When that happened, the head pressure went sky high and the a/c hoses had popped. The cure was to put thin, die cut rubber panels in front of the condensor (on the sides between the headlight supports and on the bottom between the grille and the lower condensor; there was already a "yoke seal" that sealed between the hood and the core support) such that only "normal" air could enter the grille area. They also added a "Thermostatic Ignition Control" valve via a new thermostat housing. When the engine got too hot at idle, it'd move the vacuum advance vacuum from ported (no vac advance at idle) to full manifold vacuum (so the engine rpm would increase and the added fan speed would help cool the motor and the condensor down some)! .

One other thing my friend noted was that all of the old oil needed to be removed from the system. It would react with the new R134a (and it's different oil), congeal, and find the lowest spot in the system to settle out. That usually was the bottom of the existing condensor, further reducing it's heat exchanging capacity. I knew then that modern chemistry would result in more universal and more tolerant oils, but I would suspect that the best thing to do would be to, as he suggested, flush the system via the recycling machine with liquid freon to get all of the old oil out, then refill everything with the appropriate freon and oil. I know others have reported good results without going that far, which is good.

Question from Simo:

What kind of oil is there in the AC system. Was the oil originally same kind of in '67 Imperial and '90 LeBaron?

In my Imperial all the AC rubber O-rings are bad, I think. Can they be replaced with the O-Rings which are suitable for hydraulic-systems? Material ? Neoprene?. Or is there a seal-kit available for the Chrysler AC-systems?

The AC system was four five Months disassembled from the car. That time the car was garaged and not in use.  Will there be any problems with the humidity inside the system? Is there something to do?



From Dave:

Yes the seals are available from your local Chrysler dealer, or through Direct Connection.  With the system having been open for so long, there is a non-expensive way to ensure that you have removed all of the atmospheric moisture from the system, once you have replaced all of the seals, hoses, etc.

You will have to flush the system anyway (your local automotive refrigeration shop will know how to do this, and have the proper equipment), so when you get ready to draw the final vacuum on the system prior to re-charging, first round up all of the clip-on work lights you can find, place them to shine on the condenser, compressor and the receiver/dryer (located in the compressor discharge line in one front corner of the engine compartment).

Start your vacuum with a good set of gauges attached to the system (the vacuum pump gets connected to the center hose of the gauge set just like the R-134 can will) and both high and low side valves open. About every hour or so, for the first 4 or 5 hours shut both valves and watch the low side (vacuum) gauge to make sure that whatever you've got so far is holding.

If the gauge indicates pressure increasing after 4 or 5 hours of repeating this, then you probably have a leak somewhere. (Remember to re-open the valves after each check) If the vacuum is holding, then let the vacuum pump run for 24 hours to ensure good evacuation/dehydration of the system. You are then ready to charge. Shut both valves on the gauge set and connect your refrigerant source to the center hose.

Tip the can or bottle upside down (or open the liquid valve if using a Dial-A-Charge) and purge the center hose by momentarily cracking the center hose fitting at the gauge manifold. (Be sure to have safety glasses and gloves or a rag over the fitting when you do this) Allow the hose to blow a small amount of refrigerant out and then re-tighten the fitting. This removes the air from the hose. If using cans, keep it upside down, and open the high side valve and allow the can to flow into the high side.

When it is near empty, shut the high side valve, start the car and turn on the A/C. WARNING! DO NOT run the A/C with the high side valve open as this will connect the discharge of the compressor directly to the refrigerant can! (Definitely not good!) Crack open the low side valve and allow the cycling clutch switch to pull the rest of the first can into the system and shut the low side valve.

Connect the second can to the center hose (you'll have to purge it again) Tip the can right side up this time and and allow the system to pull refrigerant into itself until the discharge pressure peaks at around 300 psi and the low side gauge cycles between the cutout point (between 25 and 40 psi) and the cut-in point (between 35 and 60 psi).

At first the clutch will cycle fairly quickly (every couple of seconds or so) but as the system approaches full charge, it will run longer and, if you have left the windows open and the blower on high, will eventually run continuously. Don't try to charge until you get rid of the bubbles in the receiver eye with R-134A. If you do you will over-charge the system. Bubbles are normal under high heat load. Once it is running continuously, check your vents. If they are cold, shut the windows and lower the blower to medium.

While you are waiting for the interior to cool down, check under the car and make sure that the evaporator drain is clear. (You'll see water dripping under the car if it is) If not you'll have to clean it out, or your carpet will get wet and your evaporator will freeze up. Once the interior is cool, then the bubbles will disappear. 

From Mikko:

>What kind of oil is there in the AC system. Was the oil originally same kind of in '67 Imperial and '90 >LeBaron?

I just called my friend who works with AC systems. When you use R134A you have to change the oils. You have to use synthetic oils because R134A doesn't dissolve with mineral oil. The old R12 includes chlorine, so you have to flush the system very well. 

>In my Imperial all the AC rubber O-rings are bad, I think. Can they be replaced with the O-Rings which >are suitable for hydraulic-systems? >Material ? Neoprene?  Or is there a seal-kit available for the Chrysler >AC-systems?

No you can't use any other O-rings. The O-rings have to be meant to work with the R134A. You local A/C store should have the correct O-rings.

Question from Leo (1967):


I checked with a local Mopar dealership yesterday about a retro kit for my air conditioning on the '67. They said that they've been putting in R134 into R12 systems without modifications. They've worked fine, no leaks, cold air and nothing has blown up. Is this believable?



From Dick:

This "could be done, but it would be wrong", to quote my namesake Tricky Dick. Also, at least in the US of A, illegal.

As a minimum, to avoid contamination of some future service person's equipment, the fittings should be changed over to the R134 type. In addition, the older hoses won't contain the R134 for long, as the molecules of the refrigerant are smaller, and will migrate through the old style hoses. Also, the system requires compatibility between the lubrication oil and the refrigerant, or the compressor will no receive adequate lubrication. Thus the oil has to be flushed and changed to the new type.

I know one could get away with this approach for a little while, but sooner or later you'd have a mess on your hands, I advise against this "shortcut".

From Don G.:


I did this a couple of weeks ago to my 1977 Ford pickup truck.  I picked up a conversion kit at Wal-Mart for $35.00.  It included fittings for the service ports, a can of lubricant and three cans of R134 refrigerant, and a valve and hose to transfer the contents of the cans into the air conditioning system. They say that the new lubricant and refrigerant will be compatible with any of the old R12 and lubricant that may be left from what was previously in the system. Nothing needs to be done to the air conditioning system itself.  There are no adjustments or component changes.  The system should be evacuated before filling.  I have a vacuum pump so I didn't take it to anyone for that service.  To be environmentally correct all R12 that is left in the system should be removed with the use of proper recovery equipment.  I ended up using the gauges that I normally used for R12 so that I could check the high and low side pressures.  They recommend only filling the system to 85% of the R12 charge.  One other fellow in the air conditioning business recommended only 75% of the R12 charge. After evacuating the system it is refilled in the normal manner with the new materials supplied with the kit. I followed the instructions which came with the kit. I monitored the pressures.  They stayed in the normal range for that system. I could have done the entire procedure without using the gauges at all.  So far the system seems to be working normally and I have been staying cool on hot afternoons. I will have to wait for long term results.  I am pleased so far. I wouldn't just change the refrigerant in my Imperial until there is some need to recharge it. This seems to be a much more cost effective procedure than paying sky high taxes on R12.  I have found that my Imperial air conditioner has more cooling capacity than it ever really uses so even if there is some loss of efficiency with the R134A refrigerant I doubt that you would ever notice it. 


From Don S.:


It seems there was a lot of hysteria when R134 first came out. You couldn't do this or that with either R12 or R134.  A friend of mine works in an A/C shop and they've done a lot of experimenting on both systems.  It seems they are more compatible than the regulators would want us to believe.  He's told me that they've topped off R134 systems with R12 with no long term side effects and it cools just as good. 


From Dave:


Air conditioners can be very tricky to retrofit. I just tried to do the one on my 87 Delta 88 with no success. I was told that 134a would work with no changes. I replaced a bad compressor myself to save money. I then vacuumed the lines. When the 134a was but in, the high pressure line was cold before the evaporator coil and the accumulator was warm. It turned out that the orifice/strainer clogged up. Since this took more savvy than I had, I took it to Pep Boys and got the complete retro. They replaced the orifice and the accumulator. Then they blew out the lines to remove as much residue, which apparently came from the old compressor, as possible. Then they charged the system. It worked great for a week. Then it cooled less and less. I took it back and they replaced the orifice again, blew out the lines and recharged it. This was done under warranty. Two weeks later the same thing happened. I took it back expecting the same problem. That was not the case. It seemed the new compressor was now leaking. I bought it at Salvos. I would have to take the car home to replace the compressor myself to take advantage of the warranty or have them do it with their parts which they would warranty with labor. I decided I didn't want to start the sequence all over again and had them replace the got it back today. Time will tell if the system works. I strongly suggest you leave it to the pros and let them have the headaches. I cost myself $250 more by trying to save a buck.

Question from Demetrios (1968):

My '68 LeBaron used to run Freeze 12. However, over the past winter, it lost charge. Nobody in town carries Freeze 12 (that is except one mechanic that I have reasons not to visit). I am considering converting to 134. A local shop quoted $250. I am wondering if I can do this myself and save some $. Anybody knows of a conversion kit for these cars? Has anybody installed it?

Reply from Dick:

AutoZone, and probably other similar stores, carries a conversion kit for about $35, and it has everything you need, including the refrigerant. I've used it successfully on 3 cars now, no problems.

Follow-up question from Brad:

What is the longest period of time you have had 134 in a car that was converted from R-12? I filled my 78 with 134 last summer and it worked great. I've only heard people say that in time it could cause trouble. I just am wondering how long it has been tested.

How do you go about "vacuuming the system"? How do you pressurize it to test for leaks? How do you detect a small leak?

Reply from Dick:

I converted my '55 Hudson about 3 years ago, and my '56 Packard about 2 years ago - both are still cooling well.

My son converted his '94 Jeep about 3 years ago also, and it is still working well.

In all of these conversions, I first vacuumed the system and checked for leaks - and fixed the ones I found. I did not replace the original hoses (they were not leaking). I had a bad evaporator valve (leaker) in the Hudson, my son had dumped the R-12 by mistake as he was pulling his engine for a rebuild, and the Packard has apparently a very slow leak (like 3 or 4 years to go down) which I have been unable to find. The 134 doesn't seem to make it any worse. I drove the Packard today, and ran the AC, as it was a very warm day, and it's still cooling fine.

Any AC repair shop will have a vacuum pump and a leak detector. (I have this equipment from the days when I ran a shop).

You can make a vacuum pump from an old compressor, as I described to D-squared, but a leak detector is another story. You will have to beg, borrow or steal one, or take it to an AC shop and ask them to test the system for you. It is possible that an auto parts store may have one to loan - as the AutoZone chain does in this area.

Very small leaks are almost impossible to find. When R12 was cheap and plentiful, if the leak was no worse than one 14 oz can every couple of years, we just ignored the leak and topped up the system when needed. With R134, we're back in the same situation again, so if your leak is no worse than the above, I'd just ignore it. If it is worse, you should be able to track it down with a good leak detector (mine is from Snap-On, but there are other good brands). These cost about $600, so this is not a cheap thing to contemplate buying.

Reply from Kerry:

Harbor Freight sells a venturi style Vacuum pump for just a few bucks (less than 20 I think). It requires an air compressor but will pull about 26 inches of mercury. A good vacuum pump will pull 28. I got a Robinaire pump from Ebay for about 120 bucks and love it. The HF thing will work though and R134 is cheap if you have to have it redone.


Question from Andrei (1974):

In the instructions for the new compressor I just purchased, it is written that it is suitable for R12 and R134a. Is this possible?


From Mike:

You will get a TON of opinions about R12 versus R134a on this list, esp. now that cooling season is here. But here's the facts: There is no direct drop-in  replacement for R12 as of this date. R134a can be used IF: The system is evacuated of all R12 and oil.  The filter dryer is replaced.  There are no leaks in the system.  The system is drawn down to a 30" vacuum, or about 500 microns.  

You then charge the system with R12 mingled with the proper oil. Pep Boys sells both R134a and the proper oil...ask them to find out what oil to use (I generally work around R22, a commercial refrigerant, so I'm not up on the proper oil to use). 

Some people will tell you that they've just charged up R12 systems with R134a and "it works great".  I don't dispute their experience, but they are rolling the dice- it may work, but it shouldn't, and there will probably be long-term problems.  The oils aren't compatible, the refrigerants themselves have different properties, and God forbid they ever take it to a professional to have any work done on it. 

Also, some converted cars don't cool as well with R134a, because its condensation point is higher than  R12. But, on an Imperial which already has a hugely over-designed cooling system, it isn't a problem. I replaced the filter dryer, compressor, and clutch on my '67, had a vacuum drawn and charged it up with R134a and it cools very well.

Follow-up from Bob:

FR-12 is an ideal replacement for R-12 and just this year I'm learning that R-134a is being replaced by this refrigerant, (by private owners), because of it's lower high and low side pressures, compatibility with internal components and general friendly properties. Also, the government will soon be ordering the auto builders to phase-out R-134a, but I don't know, yet, what the new one will be

From Allan:

On freon R12 replacement. Most of the guys I have talked to have had very good results with R406. It is sold under different brand names but is compatible with mineral oil which is what is in the R12 systems. You use less of it and the temperature at the evaporator is actually colder. You must charge it into the system as a liquid because it is a blend of different refrigerants. I have not tried it yet but intend to very soon. You must remove any R12 that is in the system now and follow the chart for the proper amount to use. Also, don't forget to clean your condenser, preferably with a good coil cleaner available at a refrigeration supply. When I was doing A/C repairs on customers cars and did this, the temperature at the ducts used to drop by almost 10 degrees on most cars because of the better heat transfer due to a clean coil. The high side pressure would drop as well which was an added benefit.

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