Hot Engine Test

HOT OPERATION
Bleed Valve Open, manifold vacuum bleeds off.
Diaphragm Internal spring pushes down on control door.
Air Control Door Falls, outside air enters air cleaner. (Heated air blocked).
Check Valve Prevents vacuum loss at full throttle.
Fixed Orifice Prevents rapid pressure changes. Allows smooth operation of control door.

Fig. 42 Air Control Door Blocking Heated Air:

HOT ENGINE TEST

1. With the air intake duct disconnected from the air cleaner snorkle, start the engine and warm up to normal operating temperature (cooling fan should cycle ON and OFF at least once).
2. The air control door should be in the down position, (blocking the heated air duct), Fig. 42.
3. If the air control door is not down, disconnect the vacuum hose from the air control diaphragm and check for vacuum. No vacuum should be available.
a. a. If vacuum is available, check the #8 vacuum hose for correct routing. If the vacuum hose is OK, replace air bleed valve A, and re-test.
b. If no vacuum is available, remove the air control diaphragm and check the movement of the air door. If the door moves freely, replace the air control diaphragm valve and re-test.