LEDs Flashing - A/C Calibration/Diagnostics and Cooldown Test

Perform this procedure when the battery has been replaced or recharged and the LED displays need to be reset.

GENERAL INFORMATION
If the Heating Ventilation and Air Conditioning (HVAC) control module is replaced, the Calibration Diagnostic and Cool-down tests will need to be performed. Once this group of tests have successfully passed, they can be performed individually. The engine must be running during the test to provide hot coolant for the heater, A/C compressor operation and to assure that the actuators are calibrated correctly. The HVAC control module is capable of troubleshooting the system in approximately 120 seconds. If a condition is detected, an error code is displayed. The error code cannot be erased until the condition is repaired and the diagnostic test is performed. Check wiring before replacing components.

Fail Codes/Level are displayed using the REAR WIPER and INTERMITTENT LED's flashing in the sequence indicated below. The REAR WIPER LED represents the Level and the INTERMITTENT LED represents the Value. After Calibration/Diagnostics is completed, the control will begin flashing Level 1 codes. Depressing the WASH button will cycle to Level 2, depressing WASH again will cycle to Level 3. Each time the WASH button is depressed will cycle to the next level. After Level 5 is reached, you will cycle back to Level 1. If the Control is a Heater Only you will only cycle from Levels 1 to 3.

For the procedures on troubleshooting these flashes, refer to Heating and Air Conditioning, Testing and Inspection, Procedures. Testing and Inspection

CAUTION: Do not remove the actuators from the Heater-A/C unit assembly with power applied. Removal should only be done with the Ignition OFF. The actuators have no mechanical stops to limit the travel. If the actuator rotates and is not connected to the unit assembly, it will become out of calibration.

Radio Bezel and HVAC Control:

Radio Bezel and HVAC Control w/Rear Blower and Zone Control:

ACTUATOR CALIBRATION
Mode, Blend and Zone (if equipped) door calibration compensates for mechanical variations in the actuators, HVAC control module and its linkages. In vehicle calibration can be entered from the control's front panel. If the REAR WIPE and INTERMITTENT LED's flash simultaneously when Ignition is cycled ON, the actuators have not been calibrated or during the previous calibration a failure occurred. Diagnostics will always occur during Calibration Diagnostic and Cool-down test.

DIAGNOSTICS
During the Actuator calibration, diagnostics are performed on the actuators and evaporator temperature Fin Sensor.

Once diagnostics are completed the REAR WIPER and INTERMITTENT LED's will flash to indicate either a successful calibration or the appropriate fail code(s). At this time manual testing of the Blend, Mode and Driver (if equipped) potentiometers can be performed. If a failure is detected during Diagnostics a fault will be set in the control. When Ignition is cycled OFF and then ON or Diagnostics is aborted, the REAR WIPER and INTERMITTENT LED's will flash simultaneously showing that a failure has occurred. The control will not indicate the fail code, but only that a failure had occurred during the last diagnostics test. The only way to clear the failure codes is repeat the Calibration Diagnostic and Cool-down test, after all repairs are completed.

COOL-DOWN TEST
This test has been designed for performance testing of the A/C system at the manufacturing facility. If the HVAC control module is replaced, the Cool-down test will occur during Calibration test. During the Cool-down test the control will monitor the temperature of the Fin Sensor. The A/C system must be able to bring the evaporator temperature down a predetermined minimum amount in less than 2 minutes.

NOTE: Cool-down will not occur on Heater Only units.

CALIBRATION/COOL-DOWN LED DISPLAY CODES

Calibration/Cooldown Test LED's:

NOTE: See chart for definition of flashing LED's. If no problems are found, the control functions normally.

CALIBRATION/DIAGNOSTICS TEST ENTRY
TO INITIATE TESTS:
^ Set Blower motor ON HIGH
^ Set Mode position to Panel
^ Open all A/C outlets
^ Set Temperature to Cold (Both slide pots if equipped)
^ Depress WASH and REAR WIPER button simultaneously for 5 Seconds (Until all LED's light)

RESULTS:
^ All LED's will turn on for 5 Seconds
^ Calibration Test is running when REAR WIPER and INTERMITTENT are alternately flashing. Cool-down test is running if A/C and RECIRC are alternately flashing.
^ Acceptable result is REAR WIPER LED is the only LED flashing. Push Rear Wiper to exit.
^ After all tests have passed, Calibration Diagnostics and Cool-down can be run separately.

If problems are found during Calibration see Actuator Calibration/Diagnostics and Cool-down Test. Testing and Inspection