Bronco L6-300 4.9L VIN Y 1-bbl (1983)
Thermostatic Air Cleaner Vacuum Switch: Description and Operation
Fig. 1 Bi-metal switch
AIR TEMPERATURE CONTROL SENSOR
A vacuum operated duct valve with a thermostatic bi-metal switch, Fig. 1, is used. The valve in the duct assembly is in an open position when the engine
is not operating. When the engine is operating at below 75° F, manifold vacuum is routed through the bi-metal switch to the vacuum motor to close the
duct valve allowing only heated air to enter the air cleaner. When the engine reaches normal operating temperature, the bi-metal switch opens an air
bleed which eliminates the vacuum and the duct valve opens, allowing only cold air to enter the air cleaner. During periods of acceleration the duct valve
will open regardless of temperature due to the loss of manifold vacuum.
