Thermostatic Air Cleaner: Testing and Inspection

1. Disconnect the vacuum hose from the upper port of the temperature regulator valve. Apply vacuum to the fitting. With the engine cold, the valve should allow vacuum to pass and act upon the flapper valve. Once the engine warms up, the valve should block the vacuum, prohibiting movement of the flapper valve.
2. Remove the hose from the lower vacuum fitting. Apply vacuum to this fitting. The flapper valve should operate. If it does not, replace the lower filter housing.
3. If the intake air preheat system did not pass step 1, but passed step 2, replace the temperature regulator valve.