Vacuum Operated Duct Test
- Apply parking brake and block wheels. Remove cover and element from air cleaner. Inspect the heat riser tube for damage and check to make sure it is properly installed. Remove components necessary to make sure that the duct door is open to fresh air. Check for binding.
- Check vacuum source and condition of vacuum hoses to bi-metallic sensor, cold weather modulator and vacuum motor. Start engine. If the duct door has moved to closed to the "heat on" position, go to step 5). If the door stays in "heat off" position, (closed to warm air), block the bleed of the bi-metallic sensor.
- Duct door must move rapidly to the "heat on" position. If the door does not fully move to cold weather modulator position, replace vacuum motor and repeat test. With engine off, cool bi-metallic sensor and cold weather modulator by spraying with refrigerant for 20 seconds. DO NOT spray when engine is running or poisonous gas will be created.
- Restart engine. Duct door should move to the "heat on" position. If door fails to move or only moves part way, replace sensor. Cool cold weather modulator and sensor.
- Start and run engine for less than 15 seconds. Duct door should move to "heat on" position. Shut off engine and watch duct door. On all vehicles without cold weather modulator, the valve should return slowly to the "heat on" position.
- On all vehicles with cold weather modulator, the valve should stay in the "heat on" position for at least 2 minutes. If it does not stay for 2 minutes, replace the cold weather modulator and repeat this step after cooling cold weather modulator and sensor.
AIR CONTROL DOOR CLOSING VACUUM
| Application | Vacuum In. Hg |
|---|---|
| Ford Motor Co. | 16 |