ture control in high position). The fuel valve will open and spray from nozzle can then be examined.

CAUTION

Have a fire extinguisher at hand and avoid any possibility of igniting the spray. NEVER attempt to burn this assembly in the open.

38. HEATER GETS TOO HOT

This trouble can be caused by a poorly adjusted thermostat or insufficient fresh air. To test thermostat, connect a test light between white terminal of ignition unit and ground. Start heater with engine running. After heater warms up, the test light should go on and off as thermostat cycles the heater on and off. If the heater cycles, but test light remains on, it is an indication that thermostat contacts are remaining closed and heater is cycling on overheat switch. Install a new thermostat to correct this condition. The fresh air supply should be checked before replacing thermostat since proper thermostat action is dependent upon an adequate supply of fresh air through heater system. Insufficient air flow can be caused by defective fresh air blower motor or by an obstruction in fresh air system. Distributive ducts door must be open at any time heater is in use. Door is controlled by temperature lever on instrument panel.

39. HEATER WORKS INTERMITTENTLY

b. Another cause of intermittent operation is air lock in heater fuel pump caused by small air bubbles in fuel. To correct this condition, inspect the heater fuel take-off tee in engine fuel pump. If heater fuel line comes off at top, remove fittings from fuel pump and reinstall them so that the heater fuel line is attached at the bottom. This will prevent bubbles from entering fuel pump. Tighten all fittings carefully and bleed fuel line after it is attached to heater fuel pump.

40. HEATER CAUSES ODOR

a. If odor is raw gasoline, the fuel connection at burner casting is leaking or solenoid valve is not tight on casting. Check and tighten leak. A slight odor when a new heater is first turned on should be disregarded.

b. If odor is burned gasoline, the exhaust tube under heater is leaking and must be repaired.

41. TOO MUCH SMOKE FROM HEATER

Excessive smoking and carbon are caused by a slow combustion air motor or a defective nozzle. Check these causes and repair or replace as required. This condition could also be caused by delayed ignition, resulting from spark plug electrodes which are badly burned, out of adjustment, or shorted with carbon. Check plug- gap. It should be .085 inches and the electrode should be reasonably clean and approximately centered in insulator of spark plug. Bend the ground electrode when making adjustment.

42. HEATER MAKES NOISE WHEN STARTING

a. If heater "pops" or "spits" when starting or cycling, it is an indication that fuel is being admitted to burner that is not being instantly ignited. This can be caused by a leaking solenoid valve seat or plunger which will permit fuel to flow in the "off" position. Another possible cause is low fuel pressure from a defective pump, or a combination of low fuel pressure and insufficient combustion air caused by a slow burner blower motor.