HVAC MTC

B1079-CLIMATE CONTROL COOL DOWN TEST EXCESSIVE TIME

For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.

Theory of Operation

The HVAC Cooldown Test checks A/C system performance based on Evaporator Temperature Sensor input. The main criteria is to lower evaporator temperature 11° C (20° F) within one minute. Before starting the test, the evaporator temperature must be above 18° C (65° F) and the blower speed must be set to high speed. When the test is running, A/C Select and A/C Request will be on and the A/C status indicator will flash. When the test is complete, the scan tool will display one or more test status messages to indicate the outcome of the Cooldown Test.

- When Monitored:
When the Cooldown Test is executed.

- Set Condition:
If the A/C system is unable to lower the evaporator temperature 11° C (20° F) within one minute.





Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

1. DIAGNOSE COOLDOWN TEST STATUS MESSAGES
1. To perform the HVAC Cooldown Test the following parameters must be met:
- The work area ambient temperature must be above 15.6° C (60° F) and the evaporator temperature must be above 18.3° C (65° F) in order to test A/C system performance.
- Verify that the mode setting is not in a defrost position and that the A/C compressor is not running. If the compressor is running, turn the A/C off and allow the evaporator to warm up before proceeding with the test.
- Set the mode to the Panel position.
- Verify that the front blower motor operates correctly in all speeds. Diagnose and repair all blower related faults before proceeding with this test. If no blower motor problems are found, set the front blower speed to high.
- With the scan tool in HVAC, select System Tests and then select Cooldown test. Allow the test to run to completion.






Were there any status messages present after performing the Cooldown Test?

Yes

- Go To 2

No

- Go To 3

2. DIAGNOSE COOLDOWN TEST STATUS MESSAGES

Pick one that best describes your Test Status Message?

Successful Cooldown - Test Passed

- Indicates that the main test criteria was met. No further Cooldown testing is necessary.

DTC Set During Routine - Test Not Passed

- With the scan tool, check for PCM and HVAC DTCs. If PCM DTCs are present, perform those respective test first.
- For PCM DTCs Testing and Inspection
- For HVAC DTCs Testing and Inspection

Conditions Too Cold - Test Not Run

- Verify that the work area ambient temperature is above 15.6° C (60° F). If not, move the vehicle to a warmer work area. Verify that the evaporator temperature is above 18° C (65° F). If not, start the engine and turn the A/C compressor off. Set the blower to high speed and allow the blower to run for five minutes. Cycle the ignition and run the Cooldown Test again.

Blowers Not On High - Test Not Run

- Set the blower speed to high speed and then run the HVAC Cooldown Test again.

Refrigerant Temperature Sensor Error

- Testing and Inspection Perform the appropriate diagnostic procedure.

No Results Stored/Test Not Complete

- Verify that power is not interrupted while rerunning the HVAC Cooldown Test and run the HVAC Cooldown Test again.

3. CHECK FOR DTCS IN THE A/C HEATER CONTROL MODULE
1. With the scan tool, read HVAC DTCs.

Are there any other HVAC DTCS present?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Go To 4

4. CHECK FOR DTCS IN THE PCM
1. With the scan tool, read PCM DTCs.

Are there any PCM DTCs present?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- For additional HVAC Cooldown Test related diagnostic information and testing procedures. Component Tests and General Diagnostics
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.