1. Wiper Switch Stalk (Most Likely Culprit):
* Problem: The switch itself might be malfunctioning, stuck in the "on" position, or have a short circuit. This is a common cause of this symptom.
* Troubleshooting: Try gently wiggling the wiper switch stalk while it's in the "off" position. A temporary improvement suggests a faulty switch. If wiggling it makes the wipers stop, replacement is highly likely needed.
* Solution: Replacing the wiper switch stalk is the most probable fix. This is often a relatively simple DIY repair (though access can vary by vehicle), but you may need a repair manual or video guide specific to your Avalanche model year. You'll likely need to remove the steering column cover to access it.
2. Wiper Motor Relay:
* Problem: The relay that controls power to the wiper motor may be stuck closed. Relays are inexpensive electromechanical switches.
* Troubleshooting: Locate the wiper motor relay in the fuse box (under the hood or inside the cabin – consult your owner's manual). You might hear clicking if you try to cycle the wiper switch. A stuck relay might not click at all. Try swapping the wiper motor relay with a similar-looking relay (one of the same amperage rating) to see if the problem moves. If the wipers now stop working when the "off" position is selected on the switch, it's likely your wiper motor relay is at fault.
* Solution: Replace the faulty relay with a new one. Auto parts stores sell relays for a very low cost.
3. Wiper Motor (Less Likely):
* Problem: Although less likely, a failing wiper motor could internally short and remain powered even when the switch is off.
* Troubleshooting: This is less likely because you'd usually experience other symptoms (like erratic wiper speeds or noisy operation) before the wipers completely failed to turn off.
* Solution: Replacing the wiper motor is a more involved repair and should only be considered if the switch and relay are ruled out.
4. Wiring Issues (Least Likely):
* Problem: A short circuit or damaged wiring could continuously supply power to the motor.
* Troubleshooting: This requires a multimeter to check for power at the motor and relay when the switch is in the "off" position. This is more difficult for the average DIYer, but a mechanic can diagnose this.
* Solution: Repair or replace any damaged wiring.
Before You Start:
* Disconnect the battery's negative terminal: This is crucial for safety before working on any electrical components.
* Consult a repair manual: A repair manual specific to your 2004 Chevy Avalanche will provide diagrams and instructions. You can find these online or at auto parts stores.
Recommendation: Start with the wiper switch stalk. It's the most likely culprit and relatively easy to replace. If that doesn't solve the problem, move on to the relay. Only consider the wiper motor or wiring issues if the other two possibilities are eliminated. If you're not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic.
