Thermostatic Air Cleaner: Testing and Inspection

Fig. 62 Checking TAC sensor in air cleaner:

SYSTEM CHECK

1. Check system to make sure that all hoses and ducts are connected. Check for kinked, plugged or deteriorated hoses.
2. If engine temperature is above 80° F, remove air cleaner and allow it to cool below 80° F. Place a cool wet cloth over sensor to aid cooling.
3. Install cooled air cleaner with cold air intake disconnected.
4. Start engine. When engine is first started, damper door should be closed. As engine warms up, damper door should open slowly. Some air cleaner sensors have a check valve that delays the opening of the damper door. Length of time depends on temperature, which may vary from a few minutes at 0° F to a few seconds at 70° F.
5. Disconnect vacuum hose from vacuum diaphragm and apply at least 7 inches Hg vacuum. Damper door should completely block off the snorkel passage. If not, check linkage for proper connections.
6. With vacuum still applied, trap vacuum in vacuum motor by bending hose. Damper should remain closed. If not, replace vacuum motor assembly. Failure of vacuum diaphragm motor is more likely to be caused from that linkage binding or corroded snorkel than a failed diaphragm. Check this first, before replacing the vacuum motor.
7. Reinstall the air cleaner. As the engine warms up, damper door should start to allow outside air and heated air to enter the carburetor.
8. If air cleaner operation is not as specified previously, or operation is doubtful, check sensor as follows:
a. Start test with air cleaner temperature below approximately 86° F. If engine was running recently, remove air cleaner cover and place thermometer as close a possible to sensor, Fig. 64. Allow air cleaner to cool until thermometer reads below approximately 86° F for about 5 to 10 minutes.
b. Start engine and allow to idle. Damper door should move to close the snorkel passage immediately if engine is cool enough. When damper door starts to open the snorkel passage (within a few minutes), remove air cleaner cover and read thermometer. Thermometer should read 100°-131° F. If not, sensor is malfunctioning and should be replaced.