Vacuum Motor & Temperature Sensor
- Remove air cleaner assembly from vehicle and allow to cool to room temperature. Sight through air cleaner duct and observe position of air diverter valve. It should be fully open to outside air.
- Reinstall assembly on carburetor and connect hot air duct and manifold vacuum hose. Start engine and observe position of air diverter valve. It should be fully closed to outside air.
- Move throttle lever rapidly to 1/2 to 3/4 opening and release. Air diverter valve should open and then close again. Allow engine to warm to operating temperature and observe position of air diverter valve. It should be fully open to outside air.
- If valve does not move to fully close off outside air at 83°F or less with vacuum applied, check for binding of the duct, vacuum leaks in hose connections or disconnected vacuum motor. If valve mechanism operates freely and no vacuum leaks are detected, connect a hose from intake manifold vacuum source directly to vacuum motor.
- If diverter valve now moves to close off outside air, replace thermal sensor switch. If valve still does not move to close off outside air, replace air cleaner assembly and vacuum motor assembly.