HVAC System Test

HVAC SYSTEM TEST

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

DRBIII(R) Displays No Response From HVAC
A/C Status Indicator Flashing
Go To 2

A/C Status Indicator Will Not Illuminate (Vehicles w/o EBL)
Refer to *A/C Status Indicator Will Not Illuminate -A/C Heater Control Without EBL Switch for the diagnostic test procedure.

EBL Status Indicator Flashing
Go To 5

Blower Motor Inoperative
Refer to *Blower Motor Inoperative for the diagnostic test procedure.

A/C Heater Control Illumination Inoperative
Refer to *A/C Heater Control Illumination Inoperative for the diagnostic test procedure.

Complete HVAC System Test
Go To 2

A/C System Performance Test
Go To 2

General System Operation & Function Test
Go To 3

Actuator Circuit Test
Go To 4

HVAC Door Recalibration
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 the 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 21.1° C (70° F) before proceeding. Move the vehicle to a warmer work area if necessary.
- Verify that the evaporator temperature is above 12.7° 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. If the test fails, the status indicator will continue to flash until either the test returns passed or the ignition key is cycled. When the A/C status indicator is flashing, it will not indicate A/C operating status. However, the A/C mode switch will continue to function normally. For vehicles equipped with EBL, when the A/C status indicator is flashing, the EBL status indicator will not function. However, the EBL mode switch will continue to function normally.

Start the engine.
Turn the Blower control to the high speed position.
With the DRBIII(R) in HVAC, select System Tests and then select AC Cooldown test. Allow one minute for the test to complete. One or more status messages will display on the DRBIII(R) after running the AC 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.

Q: Does the DRBIII(R) display a status message that indicates a fault has occurred?

Yes, Blower Not On High
Diagnose and repair the fault. Refer to Blower Not On High for the diagnostic test procedure.

Yes, Cooldown Test Sensor Failure
Diagnose and repair the fault. Refer to Cooldown Test Sensor Failure for the diagnostic test procedure.

Yes, Cooldown Time Excessive Fault
Diagnose and repair the fault. Refer to Cooldown Time Excessive Fault for the diagnostic test procedure.

Yes, Cooldown Test Too Cold To Start
Diagnose and repair the fault. Refer to Cooldown Test Too Cold To Start for the diagnostic test procedure.

NO: As necessary, either Go To 3, 4, or 5, or Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

3. GENERAL SYSTEM OPERATION & FUNCTION TEST

NOTE:
- If at anytime a DTC becomes active during this test, proceed to the conclusion question.
- If multiple DTCs are active, diagnose those that relate to a short circuit first.

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 DRBIII(R) 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 MAX 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 MAX panel position (single-zone).

Q: Does the DRBIII(R) 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 CIRCUIT TEST

NOTE: By running the Actuator Circuit Test, the A/C Heater Control can identify up to three door driver circuits shorted simultaneously. A Short Too Complex fault will set if more than three door driver circuits are shorted in the same direction (e.g. four door driver circuits all shorted to ground) or if two or more door driver circuits are shorted with at least one door driver circuit shorted to ignition and one door driver circuit shorted to ground. Fault messages displaying XXX Driver/Circuit Shorted to Ignition/Battery and XXX Driver/ Circuit Shorted to Ground will set on a per-driver basis. Fault messages displaying the same two drivers/ circuits shorted to ignition/battery as-well-as shorted to ground indicates that two actuator driver circuits are shorted together. To ensure a proper diagnosis, repair all Short Too Complex fault messages first, all common door driver circuit related fault messages second, and all other fault messages last. In addition, always test the door driver circuits after each repair by cycling the ignition switch and then running the Actuator Circuit Test again to ensure that no new faults exits. If not done so previously, start the engine.

With the DRBIII(R) in HVAC, select System Tests and then select Actuator Circuit Test.
Allow the test to run to completion before proceeding.

Q: Does the DRBIII(R) display any Actuator Circuit Test fault messages?

YES: Diagnose and repair the fault(s). For Single-Zone HVAC systems, refer to *ACTUATOR CIRCUIT TEST DIAGNOSTICS (SINGLE-ZONE) for the diagnostic test procedure. For Dual-Zone HVAC systems, refer to *ACTUATOR CIRCUIT TEST DIAGNOSTICS (DUAL-ZONE) for the diagnostic test procedure.
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. HVAC DOOR RECALIBRATION

NOTE: For vehicles equipped with EBL, running the HVAC Door Recalibration will cause the EBL status indicator to flash. If recalibration fails, the status indicator will continue to flash until either the system passes recalibration or the ignition key is cycled. When the EBL status indicator is flashing, it will not indicate EBL operating status. However, the EBL mode switch will continue to function normally. When the EBL status indicator is flashing, the A/C status indicator will not function. However, the A/C mode switch will continue to function normally. For vehicles not equipped with EBL, no status indicator will flash when running the HVAC Door Recalibration. If recalibration fails, the A/C status indicator will not function, however, the A/C mode switch will continue to function normally. If not done so previously, start the engine.

With the DRBIII(R) in HVAC, select System Tests and then select HVAC Door Recalibration.
Allow the test to run to completion before proceeding.

Q: Does the DRBIII(R) display any HVAC Door Recalibration fault messages?

YES: Diagnose and repair the fault(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