I have a 1990 f 150 4x4 with headlight problems.The other night after about 20-30 minutes of driving my headlights began turning on and off. I thought that I might have a loose connection at the headlight from 4 wheeling but neither light was loose. I let the truck sit for about 2 hours and then drove it home with no problems (lots of bumpy roads for about 30 minutes).When i got home i tried wiggling wires related to the headlights and shaking the truck without anything happening. I was about to shut the truck off and give up when they started turning off and on again. It seems like it is something related to heat because it has to sit for a few hours before the problem will go away for a while. I thought it might be the headlight switch and checked that out today. The harness connected to the switch was slightly melted (where it was connected to a terminal labled b2 on the switch) According to the manual the switch has an integral fuse which couldnt have blown because everything (dimmer, marker lights, and headlights). And the fuse for the headlight switch in the fusebox is fine. Im not sure if the headlight switch is the cause of the problem or just a victim. And im not to excited about getting a new switch and frying that one. Any suggestions or ideas from someone else who has had something like this happen are greatly appreciated.

 

The headlight switch has a built -in circuit breaker. That is what's cutting the lights on and off. The melted plug is probably the root cause. The connections are not tight enough and are overheating the switch, making the circuit breaker trip(it works on a heat principle).

A new plug is definitely going to be needed unless you can somehow fix the old one. The switch may or may not be ruined, but a new one would be something to consider too.

Also make sure you have no aux lighting or lights that draw more wattage than stock. This can cause and or aggravate the problem, since Ford sized the wiring barely large enough to carry the stock lights.

 

I was able to get the lights blinking again while i had the switch out from behind the dash panel and could hear it popping every time the lights went on and off. I will try putting in a new plug tomorrow and hopefully that will work.

 

I had this exact problem and decided to redo the headlight circuit using relays to switch the lights on and off because I knew I was using extra bright lamps that did aggravate the issue.

I had already replaced the switch in an attempt to fix the problem and noticed the plug being scorched then but once I replaced the switch it went away for awhile and I didn't bother replacing the plug as it looked like it would be a PITA to do and figured ( on a 93 ) I would have a hard time getting just the plug.

I was inspired to do the relay thing by some articles on this site:

http://www.danielsternlighting.com

It was pretty easy to do in a couple of hours ( including getting the parts ) and now the switch doesn't get real hot anymore and the lights are brighter than I have ever seen them. Note that Ford really was pinching pennys on the wiring, its the minimum gauge ( 16 I think ) that you could get away with, I went with 12 or 14 gauge for power to the lights.

BTW, I think replacing the plug in my case would have been a waste of time because the higher wattage bulbs were just sucking too much current through the switch and would have just burned up another plug in the process. This fix is forever and reduces the stress on an older wiring harness.

Tim

 

I have found that the lights didnt blink if I left the lows on and didnt use the highs. So i just bought a set of driving lights to replace the high beams.

 

I have a headlight switch it’s a 10 terminal and was wondering if I can a 13 terminal headlight switch would it work or no I have a 01 ford f150 4 door