* Power Window Master Switch: This is the most common culprit. The master switch controls all the windows and often the mirrors on that side. A faulty switch can cause complete or partial failure of the system. Testing this is usually the first step. Try using the passenger side window switch to operate the driver's window – if that works, the master switch is likely at fault.
* Fuse: Check the fuses in the fuse box (both under the hood and inside the car). Consult your owner's manual for the correct fuses for the power windows and mirrors. A blown fuse is a relatively easy and inexpensive fix.
* Wiring: Worn, corroded, or broken wiring is another possibility. The wiring harness runs through doors and other areas prone to wear and tear. Check the wiring harness for damage, especially around the door hinges and the rubber boots where wires enter the door.
* Power Window Regulator (Driver's Side): This mechanism moves the window up and down. If it fails, it could affect the window and potentially the mirror if they're on the same circuit.
* Body Control Module (BCM): This module controls many electrical functions in the car. A faulty BCM could affect multiple systems, including power windows and mirrors. This is a less likely cause but possible. Diagnosis would require more advanced tools.
* Ground Connection: Poor ground connections can disrupt electrical flow. Inspect the ground wires for corrosion or looseness.
* Relay: Some Taurus models may use a relay for the power windows. A failed relay is another possible cause.
Troubleshooting Steps:
1. Check the fuses: This is the easiest first step.
2. Test the passenger side window switch: See if it operates the driver's side window. This isolates the master switch.
3. Inspect the wiring: Look for any obvious damage or corrosion in the wiring harness, particularly around the driver's side door.
4. Check the ground connection: Look for a good ground connection at the point where the wiring harness enters the car's body.
If you're not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic for diagnosis and repair. Attempting to diagnose a BCM problem without the proper tools and knowledge can be difficult and potentially damaging to your vehicle.
