Pinpoint Test K: The Defrost System Will Not Shut Off Automatically

Glass, Frames and Mechanisms

Pinpoint Tests

Pinpoint Test K: The Defrost System Will Not Shut Off Automatically

Refer to Wiring Diagram Set 56, Heated Window for schematic and connector information. Diagrams By Number

Normal Operation

The rear window defrost relay, located in the Battery Junction Box (BJB), receives power from circuit CBP45 (YE). When the rear window defrost switch (integral to the HVAC module) is pressed, the HVAC module grounds circuit CH122 (WH/OG) to activate the rear window defrost relay. When the rear window defrost relay is activated, power is sent from the rear window defrost relay to the rear window defrost grid through circuit CRD06 (BN/YE). The rear window defrost grid is grounded through circuit GD149 (BK/GY).

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Rear window defrost relay
- HVAC module



PINPOINT TEST K: THE DEFROST SYSTEM WILL NOT SHUT OFF AUTOMATICALLY

NOTICE: Use the correct probe adapter(s) from the Flex Probe Kit when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

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K1 CHECK CIRCUIT CRD06 (BN/YE) FOR SHORT TO VOLTAGE


- Disconnect: Rear Window Defrost Relay.
- Disconnect: Rear Window Defrost Grid C402A.
- Ignition ON.
- Measure the voltage between rear window defrost grid C402A-1, circuit CRD06 (BN/YE), harness side and ground.




- Is any voltage present?

Yes
REPAIR circuit CRD06 (BN/YE) for a short to voltage. TEST the system for normal operation.

No
GO to K2.

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K2 CHECK HVAC MODULE OUTPUT


NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning of this system. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.

- Start the engine.
- Connect a 12-volt incandescent test light between rear window defrost relay socket pin 86, circuit CH122 (WH/OG) and rear window defrost relay socket pin 85, circuit CBP45 (YE).




- Does the test light illuminate?

Yes
GO to K3.

No
INSTALL a new rear window defrost relay. TEST the system for normal operation.

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K3 CHECK CIRCUIT CH122 (WH/OG) FOR A SHORT TO GROUND


- Ignition OFF.
- Disconnect: HVAC Module - Electronic Automatic Temperature Control (EATC) C228B or HVAC Module - Electronic Manual Temperature Control (EMTC) C2357A.
- Ignition ON.
- Measure the resistance between rear window defrost relay pin 86, circuit CH122 (WH/OG) and ground.




- Is the resistance greater than 10,000 ohms?

Yes
GO to K4.

No
REPAIR short to ground in circuit CH122 (WH/OG). TEST the system for normal operation.

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K4 CHECK FOR CORRECT HVAC MODULE OPERATION


- Disconnect all HVAC module electrical connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all HVAC module electrical connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?

Yes
INSTALL a new HVAC module. TEST the system for normal operation.

No
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. TEST the system for normal operation.

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