1. Power Window Switch:
* Check the switch itself: The rear window switch on the driver's side door panel is the most likely culprit. It's possible the switch has failed internally, specifically the section controlling the rear windows. Try using the passenger-side rear window switch (if equipped) to see if that one operates the rear windows. If it works, replace the driver's side switch.
* Switch Contacts: Sometimes, cleaning the switch contacts can temporarily restore functionality. Carefully remove the switch (search online for a tutorial specific to your Buick Century year), spray the contacts with electrical contact cleaner, and then reassemble.
2. Wiring and Connectors:
* Check the wiring harness: Inspect the wiring harness leading from the driver's side door panel to the rear doors. Look for any signs of damage, fraying, or corrosion, especially near the door hinges where the wires flex. If you find damage, you'll need to repair or replace the affected sections of the wiring.
* Door harness connectors: Check the connectors between the door panels and the car's main harness. They can become loose, corroded, or even break. Ensure they are securely connected.
3. Window Regulator Motors or Mechanisms:
* Motor failure: The motors in the rear door regulators could have failed. This is less likely if the switches and wiring are good, but it's possible. You would need to access the motors inside the doors to test this.
* Regulator failure: A more common mechanical failure is in the window regulator mechanism itself – the system of gears and cables that actually move the window glass. This usually manifests as the window not moving at all, or moving erratically.
4. Fuses (less likely, but check):
* Check the fuse box: While less common for just the rear windows to stop working, check your vehicle's owner's manual for the fuse location and rating for the power windows. Make sure the fuse(s) aren't blown.
5. Relay (also less likely):
* Some vehicles use relays for the power windows. Your owner's manual or a repair manual will tell you if your car does, and where to locate the relay(s).
Troubleshooting Steps:
1. Start with the easiest and cheapest: Check the driver's side switch first. Clean the contacts if possible. If you have a second switch (passenger side rear), use that to confirm the switch problem.
2. Inspect the wiring: Carefully check the wiring harness in the door and its connectors. Look for visual damage.
3. Test the motors (advanced): If the wiring checks out, you may need to gain access to the rear door panels to test the window motor directly using a multimeter. This requires some mechanical skill.
4. Consider professional help: If you're not comfortable working with car electrical systems, take it to a qualified mechanic. Diagnosing power window problems can require specialized tools and knowledge.
Remember to disconnect your car's negative battery terminal before starting any electrical work to prevent shorts or shocks. Always refer to a repair manual specific to your 1999 Buick Century for detailed diagrams and instructions.
