Non-Computer Aided Diagnostics

Symptom 1

Fig. 10 Computer Panel Connectors:

The computer display does not dim when the headlight switch is pulled "On" and the other electronic instrumentation displays dim properly.
1. Remove ATC computer control panel from instrument panel with wires connected.
2. Using a suitable voltmeter, check pin 10 of the 21-way electrical connector for voltage of 12 volts with the headlights on.
3. Rotate the dimmer switch while observing the voltmeter. Voltage should vary from 2 to 12 volts as the switch is rotated.
4. If voltage checks are satisfactory and the other electronic displays are normal, replace the ATC computer control panel. If voltage was not as specified, repair voltage supply circuit.

Symptom 2

If the computer does not remember comfort settings when the vehicle has been shut off and restarted, replace computer control panel and recheck system.

Symptom 3

If the ATC computer control panel buttons stick, do not function properly or the panel display icons are partly illuminated, replace the ATC control panel and recheck system.

Symptom 4

The ATC system temperature output is insufficient in the heat or cooling mode, but no failure code is displayed.
1. Ensure a proper blend-air door shaft to actuator engagement. If necessary, remove door and reinstall properly.
2. Check in-vehicle sensor aspirator with the ATC system operating as follows:
a. Place a small piece of paper over the sensor intake in the instrument panel.
b. If the paper clings to the intake grille, then system is functioning properly.
c. If the paper falls, the aspirator is inoperative, proceed to step 3.
3. Using a suitable voltmeter, check for battery voltage between the two center pins in the in-vehicle sensor. If voltage is detected, replace the sensor.

Fig. 11 Automatic Temperature Control Panel Display Symbols:

Symptom 5

If blower motor operates at high speeds and cannot be controlled with blower speed selector, no failure code is displayed.

1. Select a one bar indicated blower setting then disconnect two pin connector at power module.
2. If blower operates at high speeds, lower speed circuit (black/tan wire) is shorted. If blower stops, replace power/vacuum module.