For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Defogger Schematics
1 | Did you review the Rear Window Defogger Description and Operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Stationary Windows
2 |

1. Start the engine.
2. Depress the defogger switch.

Does the defogger grid warm?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3 |

1. Connect a test lamp across the defogger terminals.
2. Start the engine.
3. Depress the defogger switch.

Does the test lamp illuminate?

Go to Grid Line Repair or Bus Bar Lead Terminal Repair

Go to Step 4

4 | Test the defogger ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 5
5 | Test the defogger supply voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 6
6 |

1. Exchange the defogger relay with a known good relay from junction block 2.
2. Start the engine.
3. Depress the defogger switch.

Does the defogger grid warm?

Go to Step 10

Go to Step 7

7 | Test the defogger switch ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 8
8 | Test the defogger relay control circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 9
9 | Test the defogger switch supply voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 11
10 | Inspect for a poor connection at the defogger relay connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 12
11 | Inspect for a poor connection at the harness connector of the defogger switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 13
12 | Replace the defogger relay. Did you complete the replacement? | Go to Step 14 | --
13 | Replace the defogger switch. Refer to Rear Window Defogger Switch Replacement . Did you complete the replacement? | Go to Step 14 | --
14 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3