Intake Air Temperature Control System

Testing Vacuum Diaphram:

1. Ensure all vacuum hoses and the stove to the air cleaner flexible connector are properly installed and in good condition.

2. With engine cold, and ambient temperature in the engine compartment below 50°F the heat control door in the snorkel should be in the up (heat on) position.

3. With the engine warmed to operating temperature and running, check the air temperature entering the snorkel or at the sensor. When temperature is 100°F or higher the door should be in the down (heat off) position.

4. Remove air cleaner from engine and allow engine to cool down to 50°F. Using a suitable vacuum pump, apply 20 inches of vacuum to the sensor. The door should be in the up (heat on) position, if a delay valve is used in the system allow 35 seconds for the door to operate. If not, check vacuum diaphragm.

5. To test the vacuum diaphragm, apply 25 inches of vacuum with a vacuum pump. The diaphragm should not bleed off more than 10 inches of vacuum in 5 minutes. The door should not lift off the bottom of the snorkel at less than 5.5 inches Hg vacuum and should be in full up (heat on) position with no more than 8.5 inches Hg vacuum. If diaphragm does not operate properly, replace diaphragm.

6. If the diaphragm performs properly but proper temperature is not maintained, replace the sensor and repeat procedure.