* Worn or Damaged Window Regulator: This is a common culprit. The regulator is the mechanism that raises and lowers the window. Over time, the plastic components can crack, break, or wear down, leading to inconsistent operation. Sometimes it works intermittently, sometimes not at all. This is usually the most likely cause of complete failure, but intermittent issues suggest a partial failure.
* Faulty Window Motor: The motor itself can wear out or develop internal shorts that cause intermittent power. Like the regulator, this is more likely to lead to complete failure, but intermittent issues are possible.
* Wiring Issues: This is very common. Wires can fray, break, or corrode, particularly in the door harness where it flexes with the door opening and closing. Intermittent contact is very common with wiring problems. Check for broken or frayed wires, particularly near the door hinges and the rubber boot where the wires enter the car's body.
* Switch Problems: The power window switch itself can be faulty. Internal connections can become corroded or worn, resulting in inconsistent power delivery. Try switching from another window to see if the issue follows the switch or the window.
* Fuse: While less likely to cause intermittent problems, a failing fuse could create an inconsistent connection. Check the fuse box for the appropriate window fuse.
* Door Lock Actuator: In some vehicles, the power window system shares some electrical components with the door locks. A malfunctioning door lock actuator can sometimes interfere with the window's operation.
* Body Control Module (BCM): While less common, a problem with the BCM can affect the power windows. This is usually only suspected after eliminating other possibilities.
Troubleshooting Steps:
1. Check the fuse: This is the easiest first step.
2. Inspect the wiring: Look carefully at the wiring harness in the door for any visible damage. Pay close attention to the area where the harness enters the door jamb.
3. Test the switch: Try the switch on other windows. If the problem follows the switch, replace the switch. If it doesn't, the problem is elsewhere.
4. Listen for motor sounds: When you try to operate the window, listen closely for any unusual sounds from the door. Grinding, clicking, or humming could indicate regulator or motor problems.
5. Visual Inspection of Regulator: If possible, try to get a visual inspection of the window regulator mechanism.
If you're not comfortable working on car electronics, it's best to take your Grand Prix to a qualified mechanic for diagnosis and repair. Diagnosing intermittent electrical issues can be challenging. They will have the proper tools and expertise to pinpoint the exact cause of the problem.
