For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Exchange the rear defogger relay with a known good relay from the underhood junction block. Does the rear defogger grid continue to warm? | -- | Go to Step 2 | Go to Step 3
2 | Disconnect the underhood junction block connector C3. Does the rear defogger grid continue to warm? | -- | Go to Step 4 | Go to Step 9
3 | Replace the faulty relay Is the repair complete? | -- | Go to Defogger System Check | --
4 |

1. Disconnect connector C2 of the left instrument panel junction block.
2. Connect a test lamp between terminal C1 of the left instrument panel junction block connector C2 and ground.

Does the test lamp light?

--

Go to Step 5

Go to Step 6

5 | Repair the short to the positive battery voltage in CKT 293 between the underhood junction block and the left IP wiring harness junction block. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Defogger System Check | --
6 |

1. Disconnect connector C3 of the left IP junction block.
2. Connect a test lamp between terminal C12 of the left IP junction block connector C3 and ground.

Does the test lamp light?

--

Go to Step 7

Go to Step 8

7 | Repair the short to the positive battery voltage in CKT 293 between the left IP junction block and the rear defogger grid. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Defogger System Check | --
8 | Replace the left IP junction block.Refer to Relay/Fuse Center Replacement in Wiring Systems Is the repair complete? | -- | Go to Defogger System Check | --
9 |

1. Turn the ignition switch to the OFF position.
2. Use a J 39200 DMM in order to measure the resistance between terminal C5 of the underhood junction block connector C3 and ground.

Is the resistance measured within the specified range?

∞

Go to Step 10

Go to Step 11

10 | Replace the underhood junction block. Refer to Relay/Fuse Center Replacement in Wiring Systems Is the repair complete? | -- | Go to Defogger System Check | --
11 |

1. Disconnect connector C2 of the heater and A/C control assembly.
2. Use a J 39200 DMM in order to measure the resistance between terminal D of the heater and A/C control assembly connector C2 and ground.

Is the resistance measured within the specified range?

∞

Go to Step 12

Go to Step 13

12 | Replace the heater and A/C control assembly. Refer to Control Assembly Replacement in HVAC Systems - A/C Manual. Is the repair complete? | -- | Go to Defogger System Check | --
13 | Repair the short to ground in CKT 193 between the heater and A/C control assembly and the underhood wiring harness junction block. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Defogger System Check | --