1. Power Window Fuse: This is the most likely culprit. Check your owner's manual for the location of the power window fuse(s) and inspect them carefully. They might be blown or corroded. Replace any blown fuses with the correct amperage. If the fuse blows immediately upon replacement, there's a short circuit somewhere in the system.
2. Power Window Relay (if applicable): Some cars use relays for power windows. Consult your repair manual or online resources to locate and test the power window relay (if one exists). A faulty relay can cause both windows to malfunction.
3. Master Power Window Switch: This switch controls both front windows. A faulty switch is a very common cause of both windows stopping at once. Try wiggling the switch while testing the windows to see if there’s an intermittent problem. Replacement is often the solution. This is the most probable cause after the fuse.
4. Wiring Harness: Check the wiring harness that runs to both front power window motors. Look for any breaks, chafing, or corrosion in the wires, especially where the harness enters the door jambs (a common wear point). Pay particular attention to areas near the switches and the motors.
5. Power Window Motor (Less Likely): While less likely, it's possible that both motors failed simultaneously. Testing the motors requires more advanced tools and automotive knowledge.
Troubleshooting Steps:
* Visual Inspection: Carefully examine all visible wiring related to the power windows.
* Fuse Check: Always check the fuse first, it's the easiest and cheapest fix.
* Switch Testing: Try using a test light or multimeter to check the power going to the switch and coming out of the switch, as compared to a working switch (if you have one).
* Relay Testing (if equipped): If there's a relay, learn how to test it before you replace it; you can likely find a video online to show you how.
Important Considerations:
* Repair Manual: A repair manual specific to your 1991 Buick Century will be invaluable in identifying the fuse location, relay location (if present), and wiring diagrams.
* Safety: Disconnect the battery's negative terminal before doing any electrical testing or repairs to prevent accidental shorts or shocks.
If you're not comfortable working with car electrical systems, it's best to take your Buick to a qualified mechanic. A faulty ground wire is another less obvious possibility best diagnosed by a pro.
