HVAC System Test

*HVAC SYSTEM TEST

For a complete wiring diagram refer to Diagrams/Electrical.

Theory of Operation

The HVAC System Test provides a starting point in the diagnostic process by identifying the appropriate diagnostic procedure or system test to perform when diagnosing a given symptom, condition, or DTC. It also provides a means for testing the entire HVAC system by utilizing the A/C-heater control's On-Board System Tests. The On-Board System Tests can also assist in diagnosing stored DTCs.

Diagnostic Test

1. HVAC SYSTEM TEST

NOTE: Diagnose and repair all active DTCs before diagnosing and repairing stored DTCs.

Make a selection based on the symptom, condition, or DTC that you want to diagnose.

For Any Active DTC

Scan Tool Indicates HVAC Not Active On Bus

Blower Motor Inoperative

Complete HVAC System Test

- Go To 2

A/C System Performance Test

- Go To 2

Mode Switch & Door Actuator CKT Test

- Go To 3

Actuator DTC Detection Test

- Go To 4

Actuator Calibration Test

- Go To 5

2. A/C SYSTEM PERFORMANCE TEST

NOTE: The following are prerequisites of the Cooldown Test. Verify each of the following before running the test:
- If active, diagnose and repair Evaporator Temperature Sensor related DTCs before proceeding.
- Verify that the refrigerant system has an adequate charge. Check and repair as necessary before proceeding.
- Verify that the blower motor operates correctly in all speeds. Diagnose and repair all blower related faults before proceeding.
- Verify that the work area ambient temperature is above 15.6° C (60° F) before proceeding. Move the vehicle to a warmer work area if necessary.
- Verify that the evaporator temperature is above 13° C (55° F) before proceeding.
- Verify that the Mode Select control is set to the panel position.
- Verify 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.

NOTE: Running the AC Cooldown test will cause the A/C status indicator to flash.

NOTE: One or more status messages will display on the scan tool after running the Cooldown Test. These messages will clear after paging back out of this test function. Therefore, it is important to note all messages before doing so.

Start the engine.

Turn the Blower control to the high speed position.

With the scan tool in HVAC, select System Tests and then select Cooldown test. Allow the test to run to completion.

Does the scan tool display a status message that indicates a fault has occurred?

Yes, Conditions Too Cold - Test Not Run

- If running, turn the A/C compressor off. 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 13° C (55° F). If not, set the blower to high speed and allow the blower to run for five minutes. Then, run the Cooldown Test again.

Yes, Blowers Not On High - Test Not Run

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

Yes, No Results Stored/Test Not Complete

- Verify that power is not interrupted while rerunning the Cooldown Test.

Yes, Refrigerant Temperature Sensor Error

- For Dual-Zone HVAC systems, refer to B10B2-A/C COOL DOWN TEST PERFORMANCE for the diagnostic test procedure. B10B2

- For Single-Zone HVAC systems, refer to B1079-CLIMATE CONTROL COOL DOWN TEST EXCESSIVE TIME for the diagnostic test procedure. B1079

Yes, DTC Set During Routine - Test Not Passed

- For Dual-Zone HVAC systems, refer to B10B2-A/C COOL DOWN TEST PERFORMANCE for the diagnostic test procedure. B10B2

- For Single-Zone HVAC systems, refer to B1079-CLIMATE CONTROL COOL DOWN TEST EXCESSIVE TIME for the diagnostic test procedure. B1079

No

- As necessary, either Go To 3, 4, or 5, or Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

3. MODE SWITCH & DOOR ACTUATOR CIRCUIT TEST

NOTE: If at anytime a DTC becomes active during this test, proceed to the conclusion question.

NOTE: If multiple DTCs are active, diagnose those that relate to a short circuit first.

NOTE: Dual-Zone A/C Heater Controls do not set DTCs for stuck mode switches. Therefore, verify that the A/C Heater Control is not damaged and that the mode switches and status indicators function properly and repair as necessary before proceeding.

If not done so previously, start the engine.

Turn the Blower control to the low speed position.

Set the Blend control (single-zone) or Driver Blend control (dual-zone) to the full cold position.

If equipped, set the Passenger Blend control to the full cold position.

Monitor the scan tool for active HVAC DTCs while performing the following test steps.

If equipped, press the A/C mode switch on, wait 30 seconds, and then press it off.

On Dual-Zone systems, press the Recirc mode switch on, wait 30 seconds, and then press it off.

If equipped, press the EBL mode switch on, wait 30 seconds, and then press it off.

Move the Blend control (single-zone) or Driver Blend control (dual-zone) from full cold to full hot, wait 30 seconds, and then move it back to full cold.

If equipped, move the Passenger Blend control from full cold to full hot, wait 30 seconds, and then moved it back to full cold.

Turn the Mode select control to the defrost position, wait 30 seconds, and then turn it to the panel position (dual-zone) or panel / recirc position (single-zone). Wait 30 seconds before proceeding.

Does the scan tool display any active DTCs?

Yes

- Diagnose and repair the DTC(s).

No

- If you are here due to a stored DTC, it is possible that a technician may not have erased the DTC following a repair. If possible, verify if the vehicle was recently in for this type of service. Otherwise, either Go To 4 or 5, or visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals, and repair as necessary.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

4. ACTUATOR DTC DETECTION TEST

NOTE: The Actuator DTC Detection Test clears all door actuator related DTCs when the test is actuated.

If not done so previously, start the engine.

With the scan tool, select System Tests and then select Actuator DTC Detection. When the test is complete, select View DTCs.

Does the scan tool display any DTCs?

Yes, Dual-Zone

- Diagnose and repair the DTC(s). If multiple DTCs are present, beginning with the passenger blend door, diagnose and repair all short high DTCs and then all short low DTCs.

Yes, Single-Zone

- Diagnose and repair the DTC(s). If multiple DTCs are present, beginning with the common circuit, diagnose and repair all short high DTCs and then all short low DTCs.

No

- If you are here due to a stored DTC, it is possible that a technician may not have erased the DTC following a repair. If possible, verify if the vehicle was recently in for this type of service. Otherwise, either Go To 5 or visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals, and repair as necessary.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

5. ACTUATOR CALIBRATION TEST

NOTE: For vehicles equipped with EBL, running the HVAC Door Recalibration will cause the EBL status indicator to flash.

NOTE: The Actuator Calibration Test clears all door actuator related DTCs when the test is actuated.

If not done so previously, start the engine.

With the scan tool, select System Tests and then select Actuator Calibration Test. When the test is complete, select View DTCs.

Does the scan tool display any DTCs?

Yes

- Diagnose and repair the DTC(s).

No

- No problem found. However, if you are here due to a stored DTC, it is possible that a technician may not have erased the DTC following a repair. If possible, verify if the vehicle was recently in for this type of service. Otherwise, visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals, and repair as necessary.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test