Air Cleaner - Thermostatic: Operation: Notes

Most systems regulate the air inlet temperature by using air from a cool air source as well as heated air from a heat shroud which is mounted on the exhaust manifold. The duct and valve that regulates the airflow from these two sources is located inside the air cleaner, on the outside of air cleaner or remotely mounted in one of the inlet tubes. Airflow is regulated by a vacuum motor operated door. Motor operation is controlled by delay valves, temperature sensors and other vacuum controlled systems, depending upon vehicle application.

The air control door temperature sensor closes when the temperature of air entering the air cleaner is less than the calibration of the temperature sensor. This allows engine vacuum to operate the air control door vacuum motor, and warm manifold air to be routed to the intake. See Figure .

When engine vacuum is applied to the vacuum motor, the air control door closes off the intake of outside air. Air is then drawn into the air cleaner from around the exhaust manifold.

As air inside the air cleaner warms, the temperature sensor begins to open, bleeding off vacuum to the vacuum motor. As vacuum to vacuum motor decreases, the air control door begins to open.

As air control door opens, outside air is allowed to enter air cleaner assembly. When air entering air cleaner reaches a predetermined temperature, the air control door opens completely, and closes off the intake of heated air.