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General Motors THERMAC Air Cleaner: Testing

  1. Tape a thermometer in air cleaner next to temperature sensor. If temperature in engine compartment is more than closing temperature of sensor, let air cleaner cool to at least 7° below closing temperature of sensor. Install a tee in vacuum line at vacuum motor and connect a vacuum gauge in line.
  2. With engine off, control damper will be open (check visually). Install cover on air cleaner (without wing nut) and start engine. With engine at idle and ambient temperature below closing temperature of sensor, damper should close.
  3. When damper in snorkel begins to move toward open position, quickly remove cover on air cleaner and check thermometer and vacuum gauge. Vacuum should be 5-9 in. Hg when damper is closed to outside air.
  4. Replace cover and wait until damper is fully open, again note vacuum and temperature reading. Vacuum should be 3 in. Hg or less and temperature should be at opening temperature of sensor. If temperature is not within specifications, but vacuum is correct, replace sensor. If both temperature and vacuum are not within specifications, replace vacuum motor.
    NOTE: Temperature sensor is preset at factory. Do not adjust.
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