* Brake Light Switch: This is the most common culprit. The switch is activated when you depress the brake pedal and completes the circuit for the brake lights. If it's failing or stuck, it might be causing a short circuit, drawing power away from other circuits like the turn signals. A faulty switch can also cause the brake lights to stay on even when the pedal is not pressed.
* Turn Signal Switch (Multi-function switch): This switch controls the turn signals, wipers, and sometimes other functions. A malfunctioning turn signal switch is a strong possibility, especially given the lack of left turn signal. Internal wear or a short in this switch could affect multiple circuits.
* Wiring Harness Issues: Damaged or corroded wires, especially around the steering column (near the turn signal switch) or the brake pedal assembly, are likely suspects. A short circuit in the wiring harness could cause the problems you describe. Check for frayed wires, corrosion, or broken connections. Rats are notorious for chewing on car wires and this is especially possible in an older vehicle.
* Fuse or Relay: A blown fuse or a faulty relay related to the turn signals or brake lights could also be the cause. Check your fuse box (usually under the hood or in the dash) for blown fuses. Refer to your owner's manual to identify the correct fuses.
Troubleshooting Steps:
1. Check the Fuses: Start by checking the fuses related to the brake lights and turn signals in your fuse box. Replace any blown fuses.
2. Inspect the Brake Light Switch: Locate the brake light switch (usually on the brake pedal assembly). Visually inspect it for damage and try gently pressing the switch to see if it feels loose or sticky.
3. Test the Turn Signal Switch: If the fuses are good, the next likely culprit is the turn signal switch. This often requires some mechanical skill to test and sometimes replacement is needed.
4. Examine the Wiring: Visually inspect the wiring harness related to the brake lights and turn signals for any damage, corrosion, or loose connections. Pay close attention to the wiring near the steering column and brake pedal.
5. Professional Diagnosis: If you're not comfortable performing electrical work on your vehicle, take it to a qualified mechanic or auto electrician for diagnosis and repair. They have the tools and expertise to properly diagnose the problem.
It's crucial to resolve this issue promptly for safety reasons. Driving without functioning brake lights and turn signals is extremely dangerous.
