S10/T10 Blazer 4WD V6-262 4.3L (1989)
Operating Modes
The Thermostatic Air cleaner is designed to keep air entering the engine between 100~-120~F. Keeping intake air between this temperature reduces
exhaust emissions by permitting leaner mixtures and shorter choke on periods. The TAC also improves cold engine.
The thermostatic air cleaner includes a temperature sensor, vacuum motor, control damper and connecting vacuum hoses. The temperature sensor
controls the vacuum motor. The vacuum motor then operates the control damper, which regulates the flow of pre-heated and unheated air.
When engine compartment temperatures are below the calibration value of the sensor, the sensor closes, allowing engine vacuum to be directed to the
vacuum motor. The vacuum motor then closes the control damper to outside air, allowing heated air from the exhaust manifold to flow up through the
heat tube to the air cleaner.
As the temperature in the air cleaner reaches the calibration value of the sensor, it begins to open bleeding off vacuum to the vacuum motor. The vacuum
motor causes the control damper to partially open, allowing outside air to blend with heated air. This regulated air then enters the air cleaner assembly.
During periods of wide open throttle or when ambient temperatures are very high, there is not enough vacuum available to the vacuum motor to
overcome diaphragm spring tension. The diaphragm then causes the control damper to move downward, closing the hot air duct and allowing only
outside air to enter the air cleaner.
