View Full Version : Lights

10-21-2013, 08:32 PM
Is it the signal switch or a loose wire; main lights flicker when driving "at night" it started when I needed fog lamps. Not all the time, anyone Tys
John of redyellowblue

Steve Alger
10-27-2013, 09:49 PM
Shooting from the hip I would says it is probably a headlight switch. It has a breaker inside so your wiring harness doesn't melt down from overload. Running the fog lights will pull extra current and cause the headlight switch act like you are describing. They aren't too expensive.

10-27-2013, 10:21 PM
You'll need to replace the headlight switch, but pull your old one - there's three different ones.

While fixing it, upgrade to a relay harness to get the current off the switch.

Ideally, three harnesses - high, low, and fog.


Scott Long
10-28-2013, 10:18 AM
this is a common problem with these cars. With the fog lights on (which don't shine any more light on the road... they suck) it draws too much current and over time the headlight switch shorts out.

If you leave the fogs off it shouldn't do this, but you'll want to put the fog lights on their own circuit. There's a couple ways to do this. Easiest is to run a fused power wire up under the console from the battery, cut and connect to the power wire for the fog lights. Then you can run them any time with or without the headlights.

Replace the headlight switch in the dash as its been damaged.

10-28-2013, 10:39 AM
This is my personal experience. I have never had a headlight switch fail on any of my thunderbirds. I did have a multifunction/turn signal switch fail and cause this same issue on my 93. When it happend, I didnt have long before my low beams would not work at all and I had to cruise with highbeams only. Regardless of what part has failed on your car, make sure to check your pigtail connector for any physical burn type of damage. Replace it if necessary, or you will be dealing with the problem again soon.


10-28-2013, 12:54 PM
I installed a relay for the driving lights next to the battery on the core support. Then cut the factory wire to the driving lights. Attach the cut end of this wire which goes to the switch on the console to power the coil of this relay. The other terminal for the relay coil will be attached to chassis ground (-12VDC). Then connect power for the driving lights from the starter relay switched power terminal (+12VDC) through a 30 amp fuse to the relay common terminal. The other end of the cut wire which leads to the driving lights is terminated to the relay normally open terminal. Any time the headlights are on and the driving light switch on the console is in the on position, the relay will be powered up turning on the driving lights.

With the addition of the relay the driving light power goes direct to the lamps and not through the head lamp switch, multi function switch, and console switch. Have you ever noticed how warm/hot the console driving light switch gets after the lamps are on for a while? This is beacuse the power for the driving lights all go through this switch. Very poor design by Ford.

I went even one step further when I rewired my driving lights. I wired them to be on when the parking lights are on. This is the way most cars are wired now.

Good luck


10-29-2013, 12:05 AM
One correction - you want the 12V from the ALWAYS HOT not the SWITCHED side.

Since the switched side is only switched when STARTING the car, not while running ...

(For non-SC non-5.0HO non-Gen1 users, there isn't such a relay on the fender ... before you go looking for it.)