* Fuse: The most common cause. Check your owner's manual to locate the fuse for the rear defroster and see if it's blown. Replace it with a fuse of the same amperage.
* Relay: The defroster often uses a relay to switch the high current needed. A faulty relay can prevent it from functioning. These are usually located in a fuse box (often under the hood, but sometimes inside the car). You might need a multimeter to test the relay.
* Defroster Grid: The thin wires embedded in the rear window can break or become corroded. Visually inspect the grid for any obvious breaks or damage. Sometimes, a small crack isn't immediately apparent.
* Timer/Switch: The switch itself might be faulty. It's possible the switch is broken internally, preventing power from reaching the defroster elements. This is more difficult to diagnose without specialized tools.
* Wiring: A broken or loose wire in the wiring harness leading to the defroster grid is another possibility. This would require tracing the wires from the switch to the grid.
* Ground Connection: A poor ground connection can also prevent the defroster from working.
Troubleshooting Steps:
1. Check the Fuse: This is the easiest and first step.
2. Visual Inspection: Carefully examine the rear window defroster grid for any breaks in the lines.
3. Test the Switch (if possible): A multimeter can be used to check if the switch is sending power when activated. (This requires some electrical knowledge).
4. Check the Relay (if possible): Similar to the switch, a multimeter can be used here.
5. Professional Help: If you're not comfortable working with car electrical systems, it's best to take your Alero to a qualified mechanic. They have the tools and experience to diagnose the problem accurately.
Remember to always disconnect the negative battery terminal before working with any car's electrical system to prevent short circuits and injury.
