Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Relay Switch B+ Circuit | 2 | 2 | -- | -- |
Rear Defogger Relay Control | B0283 02 | B0283 05 | B0283 05 | -- |
Rear Defogger Control Circuitt | 2 | 2 | 1 | -- |
Relay Coil Ground | -- | 2 | 2 | -- |
Rear Window Defogger Grid Ground | -- | 2 | 2 | -- |
1. Rear defogger always ON 2. Rear defogger Inoperative |
When you depress the rear defogger button, voltage is supplied to the DEFOG relay coil and the HVAC control module also illuminates the rear window defogger indicator. Battery positive voltage is supplied at all times to the DEFOG relay switched input and the DEFOG relay coil is always grounded. This allows battery positive voltage from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger. Ground for the rear defogger grid is provided by G401.
When you start the engine and press the rear defogger switch for the first time, the defogger cycle lasts for 15 minutes. Further operation results in 7.5 minute defogger cycles. The defogger cycle resets to 15 minutes when you cycle the ignition to the OFF position and then to the ON position.
Window Systems Connector End Views
Rear Window Defogger Description and Operation
⇒ | If the Defogger Indicator does not illuminate, replace the HVAC control module. |
⇒ | If greater than the specified range, test for an open/high resistance. |
⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the RR DEFOG circuit fuse is open, test the relay controlled output circuit terminal 46 for a short to ground |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the Rear Defogger Grid does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the Rear Defogger Grid. |
⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the HVAC Control Module. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC Control Module. |
⇒ | If the resistance is not within the specified range, replace the relay. |
• | 30 and 86 |
• | 30 and 87 |
• | 30 and 85 |
• | 85 and 87 |
⇒ | If not the specified value, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.