ACTUATOR CALIBRATION, DIAGNOSTICS & COOL-DOWN TESTS
CAUTION:Do not remove actuators from HVAC plenum with ignition on (power applied). If an actuator rotates when removed from plenum or mode door linkage, it will become out of calibration. Always ensure ignition is off, prior to removing any HVAC actuator or linkage.
NOTE:Whenever HVAC control module, evaporator fin temperature sensor, mode doors or mode door actuator motors are replaced, actuator calibration, diagnostics and cool-down tests must be performed.
Calibration test, diagnostic test and cool-down test only need to be performed if fault exists in HVAC control module or after repairs involving the replacement of evaporator fin temperature sensor, any HVAC plenum mode door, mode door linkage and/or mode door actuator. Also, when a mode door actuator has come out of calibration. Always ensure engine is running during calibration test or cool-down test, to supply heater core with hot coolant. Always verify all actuators are properly installed and A/C system is operating as designed, to ensure actuators are calibrated correctly. If a condition is detected, a HVAC fault code is stored. Fault code will not be replaced until condition is repaired and calibration and cool-down tests have been successfully performed.
Diagnostic test is always performed when either calibration or cool-down tests are performed. If a diagnostic fault is recognized in actuator, mode door or evaporator fin temperature sensor, a fault code will be stored in HVAC control module. Any fault codes stored in HVAC control module will be retained until fault is identified, repaired or corrected and calibration and cool-down tests have successfully been performed. HVAC control module fault codes are cleared by performing calibration and cool-down tests.
If LEDs on HVAC control panel are not flashing, calibration test and cool-down test do not need to be performed. If any LEDs on HVAC control panel are flashing during normal driving conditions, a fault has been detected. Calibration test compensates for mechanical differences in actuators, actuator-to-mode door linkage, HVAC control module and travel of actuator mode doors (mode, blend, recirculation and zone/driver). Cool-down test monitors evaporator fin temperature sensor to verify A/C system performance. Check HVAC control panel button LEDs for the following possible conditions:
No flashing LEDs. System is operating as designed.
If rear WIPER and rear INTERMITTENT WIPER button LEDs are flashing simultaneously, actuators have not been calibrated, a previous calibration failure occurred or diagnostics have identified a fault. Perform calibration test. See CALIBRATION TEST.
If A/C and RECIRC button LEDs are flashing simultaneously, system has not passed cool-down test. Perform cool-down test. See COOL-DOWN TEST.
If rear WIPER, rear INTERMITTENT WIPER, A/C and RECIRC button LEDs are all flashing simultaneously, system has failed both calibration test and cool-down test. See CALIBRATION TEST and COOL-DOWN TEST.
Abort/Exit Calibration Test Or Cool-Down Test
To abort or exit out of calibration test or cool-down test at any time, cycle ignition switch off and on. From HVAC control panel, tests can be aborted or exited by pressing rear window DEFROSTER, rear WIPER and RECIRC buttons. Testing will automatically time out after about 15 minutes, from time tests were entered.
WARNING:Calibration test and diagnostics are automatically performed whenever HVAC control module detects a "new" VIN (when replacing HVAC control module). Ensure pretest conditions for calibration test have been met, prior to initial start up after replacing HVAC control module. If preconditions are not met, actuators will not calibrate correctly and HVAC fault codes may be stored.
To enter calibration test, set parking brake and ensure the following pretest conditions have been met. Start and warm engine to normal operating temperature. Evaporator should be at or about ambient temperature. With engine idling, turn blower switch to high. Turn mode switch to panel. Open all A/C outlets. Move temperature lever to full cold. After pretest conditions have been met, go to next step.
Press and hold rear WASH and rear WIPER buttons simultaneously for 5 seconds (until all HVAC controller LEDs illuminate). All HVAC controller LEDs should illuminate for 5 seconds, then all LEDs should turn off. Next, rear WIPER and rear INTERMITTENT WIPER button LEDs should begin to alternately flash, indicating calibration test is in progress. Within 60 seconds, system will indicate if a fault is present, calibration test was successful or system is ready to begin cool-down test. Observe HVAC control panel LEDs for following possible results:
If rear WIPER and rear INTERMITTENT WIPER button LEDs should begin flashing simultaneously, a fault (DTC) is present. See READING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. After faults are repaired, repeat calibration and cool-down tests.
If only rear WIPER button LED is flashing, calibration test was successful. HVAC control module is ready for manual entry into cool-down test. See COOL-DOWN TEST.
If rear WIPER and rear INTERMITTENT WIPER stop flashing, then A/C and RECIRC button LEDs begin to flash alternately, system has automatically entered cool-down test. See COOL-DOWN TEST.
If rear WIPER and rear INTERMITTENT WIPER button LEDs stop flashing, calibration test is successful. HVAC system has automatically returned to normal operation. Cool-down test is not necessary at this time. Calibration test is complete. Ensure system is operating as designed.
NOTE:If evaporator is cold, HVAC system will fail cool-down test. Prior to cool-down test, operate HVAC system with A/C compressor off, temperature lever to warm, mode selector in MIX position and blower on high for 3-5 minutes to bring evaporator to a warm or ambient temperature before performing cool-down test.
During this test, the HVAC control module will monitor evaporator fin temperature sensor. The A/C system performance must be able to bring evaporator temperature from ambient temperature, down to a predetermined minimum in less than 2 minutes.
To enter cool-down test, set parking brake. Ensure evaporator is at room temperature. Start and warm engine to normal operating temperature. With engine idling, turn blower switch to high. Turn mode switch to PANEL. Open all A/C outlets. Move temperature lever to full cold.
Press and hold rear WASH and A/C buttons simultaneously for 5 seconds (until all LEDs illuminate). All LEDs should illuminate for 5 seconds. A/C and RECIRC button LEDs will alternately flash during cool-down test. If A/C and RECIRC button LEDs begin flashing simultaneously, cool-down test has failed. Go to COOL-DOWN TEST FAILED.
After approximately 60 seconds, if only rear WIPER button LED is flashing, calibration is successful and system is okay. If rear WIPER and rear INTERMITTENT WIPER button LEDs are flashing simultaneously, Diagnostic Trouble Codes (DTCs) are present in HVAC control module. See READING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM.
Cool-Down Test Failed
During this test, actual A/C performance will be compared with the A/C performance information the evaporator fin temperature sensor is providing the HVAC control module. This will determine if evaporator fin temperature sensor is working properly. The evaporator must be at about the same temperature as ambient temperature when the test begins. When the test starts, the A/C system must bring evaporator temperature down by 20 F (7 C) in 2 minutes. This temperature is measured at the evaporator core by evaporator fin temperature sensor. This test will determine if the outlet air temperature will drop 20 F (7 C) in 2 minutes to verify evaporator fin temperature sensor is functioning correctly.
Ensure A/C system is properly charged and operating properly. See A/C SYSTEM PERFORMANCE under SYSTEM TESTS. If A/C system performance is poor or inoperative, recharge or repair A/C system as necessary before proceeding. If A/C system is operating properly, place a thermometer in left side of center outlet vent of instrument panel. Perform cool-down test. See COOL-DOWN TEST. If actual outlet air temperature drops at least 20 F (7 C) in 2 minutes, go to next step. If outlet air temperature does not drop as described, go to step 4.
If outlet air temperature drops at least 20 F (7 C) in 2 minutes, turn A/C compressor off. Place mode selector dial to MIX position. Move temperature lever to maximum warm position. Place blower motor to highest setting. Operate engine at high idle for 3-5 minutes, to bring evaporator temperature to ambient or a warmer temperature. Using scan tool, monitor evaporator fin temperature sensor input to HVAC control module and compare with thermometer. Perform step 2, then go to next step.
If evaporator fin temperature sensor input to HVAC control module on scan tool does not change in direct relationship to temperature change of thermometer, go to step 6. If scan tool and thermometer values agree, go to next step. If evaporator fin temperature sensor input to scan tool does not change at all, check for an open or shorted circuit to evaporator fin temperature sensor. See WIRING DIAGRAMS.
Perform calibration, diagnostics and cool-down tests to clear DTCs. See CALIBRATION TEST and COOL-DOWN TEST.
Inspect evaporator fin temperature sensor location and proper installation. Inspect operation of HVAC plenum mode doors, actuators and linkage. Inspect outside and recirculation air inlet for blockage or restricted air flow. Repair any fault(s) that may exist. If air flow through plenum is okay, remove evaporator fin temperature sensor from evaporator core. With evaporator fin temperature sensor next to evaporator, repeat step 2. If scan tool and thermometer values do not agree, replace evaporator fin temperature sensor or evaporator core as necessary.
Sunday, May 9th, 2010 AT 8:24 PM