Reset Procedure
GENERAL INFORMATIONIf the HVAC control module is replaced, the Calibration Diagnostic and Cooldown tests will need to be performed. Once this 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 wire before replacing components.
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.
ACTUATOR CALIBRATION
Radio Bezel and HVAC Control:
Radio Bezel and HVAC Control, Rear Blower Motor Switch and Zone Control:
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. Diagnostics will always occur during Calibration Diagnostic and Cooldown test.
DIAGNOSTICS
During the Actuator calibration, diagnostics are performed on the actuators and evaporator temperature Fin Sensor. Once diagnostics are completed the HVAC control head LED's will stop flashing to indicate a successful calibration. 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 LED flashing will stop. The only way to clear the failure codes is repeat the Calibration Diagnostic and Cooldown test, after all repairs are completed.
COOLDOWN 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 Cooldown test must be run after the Calibration test. Cooldown will not occur on Heater Only units. During the Cooldown 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.
CALIBRATION/COOLDOWN LED DISPLAY CODES
Calibration/Cooldown LED Display Codes:
See chart for definition of the flashing LED's noted before ignition cycled off. If no problems are found,the control functions normally.
NOTE: Calibration is run automatically whenever the control head detects a "new" VIN number. Calibration may be initiated manually by pressing and holding WASH and REAR WIPER buttons for 5 seconds.
COOLDOWN TEST ENTRY
To Initiate Test:
- Set Blower motor ON HIGH
- Open all A/C outlets
- Depress A/C and WASH buttons simultaneously for 5 Seconds (Until all LED's light)
Results:
- All LED's will turn on for 5 Seconds.
- Cooldown test is running if A/C and RECIRC are alternately flashing.
- Acceptable result is when LED flashing stops.
- Calibration Diagnostics and Cooldown must be run separately.
CALIBRATION DIAGNOSTICS AND COOLDOWN ABORT
Test can be aborted by doing one of the following:
- Depressing Rear Window Defogger, RECIRC and Rear Wiper buttons.
- Cycling Ignition OFF and then ON.
- Control will automatically abort after 15 minutes from the time Calibration Diagnostics and cooldown was entered.
- The HVAC control module will return to normal operation or may indicate unsuccessful Calibration Diagnostics or Cooldown test by LED's flashing simultaneously.
COOLDOWN TEST FAILURE
1. Determine if the refrigerant system is operating correctly:
- Check the outlet air temperature
- Feel the compressor suction plumbing, is it hot?
1. If not OK, go to Step 2. If OK, repeat the Calibration Diagnostic and Cooldown test.
2. If system does not seem to be operating correctly, perform diagnostics for poor performance:
- Low refrigerant charge
- No charge
- Compressor not operating
Verify that the test was done with the evaporator at room temperature. The test consists of starting the compressor and measuring the time it takes for the evaporator temperature to fall 7 °C (20 °F). If the compressor has been running, the evaporator is cold already and will not be capable of falling 7 °C (20 °F). If the test was run with a cold evaporator, turn A/C OFF and turn the blower motor switch to high position for 3 to 5 minutes till the evaporator is to room temperature. Then repeat the Calibration Diagnostic and Cooldown test.
If refrigerant system is performing properly and the system will not pass test. Repeat the Calibration Diagnostic and Cooldown test to determine if the evaporator temperature FIN sensor has developed an open or a short circuit. If the HVAC control module still passes Calibration test, verify Cooldown test manually with a pocket thermometer. The outlet air temperature must drop at least 7 °C (20 °F) within two minutes. If the vehicle passes with the manual thermometer, use the DRB III viewing the evaporator probe temperature readout, and repeat the Cooldown test. Ensure the evaporator is at room temperature before starting test. Check if evaporator probe will drop the temperature 7 °C (20 °F) in two minutes. If the Evaporator Probe is found to be faulty, check that the sensor is positioned in the evaporator fins properly. If not, correct and repeat test. If OK, replace the evaporator probe.
Once the repairs are completed, repeat the Calibration Diagnostic and Cooldown test. Repeating the test is necessary to clear the DTC's.
EEPROM DATA
Calibration Diagnostics, Cooldown Status and evaporator temperature Fin Sensor values are stored in an EEPROM memory internal to the control. The microcomputer within the HVAC control module uses this information:
- To determine if Cooldown needs to run
- For proper position of the Heater-A/C unit assembly doors
ACTUATOR CALIBRATION AND DIAGNOSTICS
NOTE: Do not run actuators unless they are properly mounted on the HVAC control module.
Actuator end point calibration takes approximately 60 seconds. The REAR WIPER and INTERMITTENT LED's will flash alternately during the test. The control will cycle the Blend actuator(s) to the Heat stop first then back to Cold. After the Blend actuator(s) have been calibrated the Mode actuator will be cycled to Defrost and then to Panel. Successful calibration is defined as actuator travel falling within their minimum and maximum limits.