Thermostatic Air Cleaner: Testing and Inspection

1. Check that all vacuum hoses and the stove to air cleaner flexible connector are properly attached and in good condition.
2. With engine cold and engine compartment temperature below 100° F on 1970-73 vehicles, 90° F on 1974-77 except 1977 Ramcharger and Trailduster, 65° F on 1977 Ramcharger and Trailduster, 80° F on 1978-79 vehicles, or 50° F on 1980-82 vehicles, the heat control door in the snorkel should be in the up (heat on) position.
3. Run engine to normal operating temperature and check air temperature entering the snorkel or at the sensor. When air temperature entering outer end of snorkel is above 104° F on 1970-73 vehicles, 109° F on 1974-77 except 1977 Ramcharger and Trailduster, 94° F on 1977 Ramcharger and Trailduster, 89° F on 1978-79 vehicles, or 99° F on 1980-82 vehicles, the heat control door should be in the down (heat off) position.
4. Remove air cleaner from engine and allow it to cool down to 90° F on 1970-77 except 1977 Ramcharger and Trailduster, 65° F on 1977 Ramcharger and Trailduster, 60° F on 1978-79 vehicles, or 50° F on 1980-82 vehicles.
5. With 20 inches Hg applied to sensor, the heat control door should be in the up (heat on) position. If not, check the vacuum diaphragm.
6. To check the vacuum diaphragm, apply 20 inches Hg to the diaphragm. On 1970-73 vehicles, the diaphragm should hold 20 inches Hg for five minutes. On 1974-82 vehicles, the diaphragm should not lose more than 10 inches Hg in five minutes. Release vacuum on the diaphragm, then slowly build the vacuum and observe door operation. The door should lift off the bottom of the snorkel at not less then 5 inches Hg on 1970-77 vehicles, or 5.5 inches Hg on 1978-82 vehicles. The door should be in the full up position with no more than 9 inches Hg on 1970-77 vehicles, or 8.5 inches Hg on 1978-82 vehicles.
7. If door does not operate properly, replace the vacuum diaphragm.
8. If vacuum diaphragm functions properly. but correct temperature is not maintained, replace sensor and repeat steps 2 and 3.