* Faulty Headlight Switch: This is a very common culprit. The switch itself might be failing internally, causing intermittent contact. The switch gets hot with use, and over time, the internal contacts can become worn or corroded, leading to this problem.
* Wiring Issues: Worn, corroded, or loose connections in the wiring harness leading to the headlights are a strong possibility, especially on a car with such high mileage. Look for chafing, broken insulation, or corrosion at the connectors. Vibrations over the years can cause wires to break internally, creating intermittent contact. This is particularly common near the headlight switch and the headlight units themselves.
* Grounding Problems: A poor ground connection can cause electrical gremlins like this. Check the ground wires at the headlight units and the battery; ensure they are clean, tight, and corrosion-free.
* Multi-Function Switch (Turn Signal/Wiper Switch): While less likely, a failing multi-function switch can sometimes affect headlight operation. If the switch controls other functions that also exhibit intermittent behavior, this could be a suspect.
* Relay Problems: Headlights often have a relay that switches the high current. A failing relay can lead to intermittent operation.
Troubleshooting Steps:
1. Visually inspect the wiring: Carefully examine all wiring related to the headlights, from the switch to the headlights themselves. Look for any signs of damage, corrosion, or loose connections. Pay close attention to the connectors.
2. Check the headlight switch: This is often the easiest and most cost-effective component to replace first, if you suspect it.
3. Check grounds: Make sure all grounding points are clean and tight.
4. Test the relay (if applicable): If you can locate the headlight relay, you can test it with a multimeter to ensure it's switching properly. A parts store or online resources can provide a diagram for your specific model to help find the correct relay.
5. Have a professional look: If you're not comfortable working with car electrical systems, it's best to take your Cougar to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and efficiently.
The high mileage on the car makes wiring issues more probable, but a failing switch is a strong contender. Systematic checking of the wiring harness and the switch itself should yield results.
