Component Tests and General Diagnostics

Test the controller circuits if system operation indicates a malfunction. Test by removing the controller from the IP and the cover from the back of the controller connector. This will permit insertion of the test probes from the back side of the connector. Use a digital volt or digital multimeter to test the controller. Do not use an analog meter to test the controller.

To Test:
1. With the ignition switch OFF, insert the positive probe into terminal 12 (circuit 2), and the negative probe into terminal 8 (circuit 150). The meter should read 12 volts. If there is no voltage, check the junction block AC fuse link.
2. Move the positive probe to terminal A (circuit 50) and turn the ignition to RUN. The meter should read 12 volts. If there is no voltage, check the AC/HTR fuse in the fuse block.
3. Insert the positive probe into terminal H (circuit 903) and the negative probe into terminal 4 (circuit 904). Set the control to DEFROST. The meter should read -7.0 to -7.5 volts. Now set the control to HEATER. The meter should now read + 7.0 to + 7.5 volts and then drop to 0 after about 5 seconds. Set the control to UPPER AIR. The meter should read +7.0 to +7.5 volts. This tests the operation of the MODE door control motor.
4. Insert the positive probe into terminal D (circuit 362) and the negative probe into terminal 11 (circuit 361). The meter should read 3.0 to 3.5 volts.
^ Set the control to HEATER. The meter should now read 1.5 to 1.0 volts.
^ Set the control to UPPER AIR. The meter should read 0.25 to 0.30 volts. This tests the operation of the feedback potentiometer in the MODE DOOR motor.
5. Insert the positive probe into terminal 3 (circuit 900) and the negative probe into terminal J (circuit 901). Select HOT. The meter should read +7.0 to +7.5 volts.
^ Set the control to COLD. The meter should read -7.0 to -7.5 volts. The meter will fluctuate as the motor steps. This tests the operation of the TEMP control motor.
6. Insert the positive probe into terminal 10 (circuit 902) and the negative probe into terminal 8 (circuit 361). The meter should read 0.5 to 1.0 volts with the control at HOT.
^ Select COLD. The meter should read 2.0 to 2.5 volts. This tests the operation of the TEMP control door feedback potentiometer.
7. Insert the positive probe into terminal 7 (circuit 905) and the negative probe into terminal 6 (circuit 906). With the ignition ON the meter should read -7.0 to -7.5 volts. Turn the ignition OFF. The meter should now read +7.0 to +7.5 volts. This tests the operation of the AIR INLET control motor. The positive and negative voltages indicate the direction of motor rotation.
8. Insert the positive probe into terminal 9 (circuit 907), and the negative probe into terminal 11 (circuit 361). The meter should move from a low reading with the ignition OFF, to 3.0 to 3.5 volts with the ignition ON. This tests the operation of the AIR INLET control motor feedback potentiometer.
9. Set the blower to LO speed. Insert the positive probe into terminal A (circuit 50), and the negative probe into terminal L (circuit 963). The meter should read 11.5 to 12.0 volts.
^ Set blower to MED. The meter should read 0 volts. Set the blower to HI. The meter should read 11.5 to 12.0 volts. Move the negative probe to terminal M (circuit 951).
^ Select LO speed. The meter should read 11.5 to 12.0 volts.
^ Select MED. The meter should read 11.5 to 12.0 volts. This test for voltage to the blower control relays. If the HI blower relay will not energize, the blower will operate at MED speed in the LO and MED positions, and there will be no HI speed. If the LO blower relay will not energize, the blower will operate at HI speed in the HI and LO positions and there will be no blower operation in the MED position. If both relays will not energize, there will be no blower operation.
10. Insert the negative probe into terminal K (circuit 966). Select A/C. The meter should read 11.0 to 12.0 volts. This will test the A/C clutch relay operation.