Heating, A/C - Poor Performance Diagnosis
NO: 24-16-95GROUP: Heater & A/C
DATE: Dec. 8, 1995
SUBJECT:
HVAC Diagnosis
MODELS:
1996 (NS) Town & Country/Caravan/Voyager
1996 (GS) Chrysler Voyager (European Market)
SYMPTOM/CONDITION:
1. A/C blows hot air on passenger side/driver side or both.
2. Air blows through defrost or panel outlets only (mode will not change).
3. Fault codes (flashing HVAC indicator lights/LED's) are intermittent without explanation.
4. HVAC control is locked in the diagnostic mode, cannot abort.
5. HVAC control suddenly goes dead (doesn't light up or have any effect on HVAC operation), skip to the Secondary Diagnosis section of this bulletin.
6. HVAC control has blinking LED's which do not correspond to a fault code.
NOTE:
If the diagnostic procedures have been exhausted with no problem found, skip to the Secondary Diagnosis section of this bulletin.
DIAGNOSIS:
With the engine running, look at the HVAC control LED's, if they match any of the combinations below perform the necessary tests as indicated.
Rear Wiper and Intermittent Rear Wiper LED's flashing at the same time:
Indicates the Calibration/Diagnostics test has failed and a failure code is stored. Run the Calibration/Diagnostics test as described on page 24-7 of the 1996 Town and Country, Caravan and Voyager Service Manual Supplement (Publication No. 81-370-6105A). The failure code will be displayed, refer to page 24-8 for the description of the failure codes/level display and "HVAC Control Diagnostic Conditions" starting on page 24-9 for a description of the diagnostic procedure for the displayed failure code.
A/C and Recirculation LED's flashing at the same time:
Indicates the Cooldown test has failed. Run the Cooldown test as described on page 24-7. If the Cooldown test fails again perform the diagnostic procedures listed for HVAC Control Diagnostic Conditions "A/C and Recirc LED flashing simultaneously" on page 24-11.
Rear Wiper and Intermittent Rear Wiper LED's flashing at the same time and A/C and Recirculation LED's flashing at the same time:
Indicates the Calibration Diagnostics test has failed and the Cooldown test has failed. Run the Calibration Diagnostics test as indicated on page 24-7. If the A/C and Recirculation LED's do not stop flashing, run the Cooldown test as described on page 24-7.
NOTE:
If the Cooldown Test is run during cold ambient temperatures, passing the test may be difficult. For the Cooldown Test to be passed, the vehicle should be brought into a service area that is at 70°F. (21°C.) or higher and allowed time to for the vehicle interior to come up to the service area temperature (running the engine with the heater on high blower, and temperature control set to full hot can help reduce the time required) before the cooldown test is run.
If no lights are flashing:
Run the Calibration/Diagnostics test as indicated on page 24-7. If a failure code is displayed, refer to page 24-8 for the description of the failure codes/level display and "HVAC Control Diagnostic Conditions" starting on page 24-9 for a description of the diagnostic procedure for the displayed failure code.
If, after performing the appropriate diagnosis listed above, a defect is not found but the HVAC still is not functioning properly:
Check the HVAC system wiring. It is possible a wire may be shorted to ground or has an intermittent connection.
SECONDARY DIAGNOSIS:
1. If the HVAC control symptom is that it suddenly goes/went dead, check for a loose/unseated 21-way connector behind the HVAC control.
2. Inspect the HVAC 14-way connector (accessible by removing the instrument panel top cover) Check each pin (except for pin 2, actuator feedback/sensor return, which is ground) of the 14-way HVAC connector for continuity to ground with an ohmmeter. If a grounded wire is discovered, locate the point at which the wire is grounded and repair the wiring (be sure to check all wires at that point for a possible grounded condition). Inspect the following areas first if a grounded 14- way connector wire is suspected:
- HVAC wiring harness 4-5 in. from the 14-way connector on the HVAC unit near the air bag bracket.
- Wiring routed between the HVAC unit and the dash panel (bulkhead). HVAC unit removal is required to access this location if the wiring was not properly routed on the HVAC unit.
3. Remove the HVAC control and disconnect it from the 21-way connector. Check each pin (except for pin 21, which is ground) of the 21-way HVAC control connector for continuity to ground with an ohmmeter. If a grounded wire is discovered, locate the point at which the wire is grounded and repair the wiring (be sure to check all wires at that point for a possible grounded condition). Inspect the following areas first if a grounded 21-way connector wire is suspected:
- The 21-way wiring harness where it is routed through the metal frame of the instrument panel behind the HVAC control.
- Looking from the driver's side floor, large bracket makes the mode door actuator of the HVAC unit difficult to access. Inspect the wiring for being pinched or cut by the bracket (if grounded wiring is discovered at this point, be sure to remove any sharp edges that may be on the bracket and repair the wiring).
Verify proper HVAC system operation by running the Calibration/Diagnostics test as described on page 24-7 after all repairs have been made.
POLICY: Information Only