Control Module HVAC: Testing and Inspection

AC Amplifier Location:

ENGINE SPEED DETECTION CIRCUIT CHECK

1. Start engine and fully warm up.
2. Engage air conditioner.
3. Verify the compressor clutch is NOT engaged from 600 - 700 rpm.
4. If the cut-off rpm is too high, turn the adjusting knob on the amplifier clockwise. If the cut-off rpm is too low, turn the knob counterclockwise to adjust.

AC Amplifier Adjustment:

TEMPERATURE DETECTION CIRCUIT CHECK


1. Remove the glove box and disconnect the thermistor connector. Connect a variable resistor which has a 3000 - 5000 ohm capacity to the harness end of the thermistor connector. (The variable resistor is taking the place of the thermistor for this test.)
2. Run the engine and operate the air conditioner to get maximum cooling. Set the controls to RECIRC, VENT, FULL COOL, and blower speed HI.
3. Adjust the resistor to force the compressor to go ON and OFF and measure the resistance of the variable resistor each time.
4. Clutch ON resistance should fall between 3800 - 4200 ohms. Clutch OFF resistance should fall between 4100 - 4300 ohms.
5. If the ON or OFF resistance specs are incorrect, turn the temperature adjusting screw until the spec. is attained.