Comanche 4WD L4-150 2.5L VIN E TBI (1989)
Thermostatic Air Cleaner: Description and Operation
TAC Heat Off Position
This system uses a thermostatically controlled air cleaner to maintain a predetermined air temperature entering the carburetor. This system is comprised
of an exhaust manifold mounted heat stove, a heated air tube, an air temperature sensor, thermal check valve, reverse delay valve, and a vacuum motor
operated air valve. The air valve can close the opening to warm or cold air, or blend a mixture of both. The air valve is in an open position when the
engine is not operating. When the engine is operating at below normal operating temperature, 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. A reverse delay valve provides approximately 100
seconds delay before allowing vacuum to close the trap door.
