I have a '91 f350 7.3d for about 5 years, we don't drive it daily, only when we need to transport a horse for showing, lessons or breeding. In the time we are owner of this truck I had to replace the main light switch for 3 times. I don't think this is normal or is it ? If anybody has a solution for this problem, I would be glad to hear it.

 

Nope, OEM light switches are supposed to last a little longer than 20 months a pop. (Well, I can't speak for Yugo....) Sounds like you're asking the switch to deal with more current flow than it's capable of handling. Real common cause of high(er) current flow is corrosion on the connectors. First, check the brass connectors inside the harness plug at the headlight switch. Make sure they're clean and bright. Put a little dab of silicon dialectric (distributor) grease in the opening of each brass connector, then plug it back in. Also look at the plug itself for signs of overheating. This will help you home in on the circuit that's pulling all those amps. Go through that circuit and make sure that every wire connection is clean and tight. Any ground connections need to be cleaned, greased and fastened tightly to the truck.

 

Due to extra lights the power requirement is much higher so visit........and solve part of the problem, also only buy OEM switches is advised.

https://www.ford-trucks.com/article/...r_Brights.html

 

A few relays and some 10 guage wire will fix the problem forever.
Plus you will have brighter headlights and they will last longer.

Should have looked at the link first. But since you tow a horse trailer you also need to do the same relay thing to the rear tail lights and the trailer lights circuit. Same deal as the headlights and the trigger wire is brown in the same harness. Be careful of which brown you cut due to the front park lights are also brown. I ran 8 guage from my relay to the back of the truck, but I have a flatbed with even more lights on it.

 

Thanks guys for your quick reply's.I looked at the link of plc7.3 an it looks plain and simple but very effective so I will try this. For the trailer exists an original relais under the hood with two connectors, can I use this or is it better to connect the trailer in another way.
By the way, the lightswitch is from MOTORCRAFT, I don't know if I can get a OEM switch in holland.

 

I wired my own relay to the battery and all the way to the back with heavier wire. The wire Ford used is way to small for the extra lights of a trailer plus the truck tail lights.

 

Dave,
I am going to do this to my truck too (because I have gone through a headlight switch since 1.5 years ago.) do you like this setup for the headlights, and considering that I pull a boat trailer (extra lights) would you do it the same or since I need to do something for the rear to do it a different way
TIA,
Charlie

 

I put all my relays behind the coolant recovery tank on mine.
I ran 12 wire for each headlight connection and to the battery for each relay as in the link above.
I also installed a third relay right beside the others with an 8 guage wire from the battery to the relay and then from the relay to the back of the truck. Right at the end of the frame I split it to the truck bed and trailer connector with 10 wire to each.
Now the only lights on my switch are the cab lights, the two front marker lights, front park lights and the insturment panel lights.
Before the end of summer the only thing that will be left on the headlight switch will be the insturment lights because I am going to put relays on everything including turn signals. And while I am at it I am getting rid of all that small wire on every light on the truck. Advance Auto had some nice heavy duty headlight pigtails with 12 guage wire on them for about 3.50 each, and I got my relays there that were rated for 30 amps for about 3 dollars each. Now all I need to find is a place to get the split wire wrap in pieces longer than 10 feet. I have lots of plans for my truck this summer if I have the time, we have a bunch of federal pay scale jobs this year, so dollars should be easier to come by for the truck unless something else goes wrong.

 

I just noticed in the newest Summit Racing: they're offering pre made wiring harness's with the relays. I think they were around $60.00

More like $40.00


Poke here

 

do they have for Ford or only Chevy???

 

It's a non-discriminating part. Just match up your type of plug/socket.

9004, 9006, 9007, or H4

 

I had a 91 F150 gas engine. It was eating light switches. Finally I realized it was because my daughter was using the lighter for her laptop computer, which got it's power from the headlight switch. I found a different source for the lighter and solved the problem. But we were not towing anything with the truck, so it was a different kind of problem.

 

I chekd the lightswitch, the trouble I have is not caused by the headlights.
When I switch the lights on the lightbleu/red and the brown wire are becoming hot and there is smoke from the switch. These wires run by the dimmer, brown is for all markers on the truck and runs to the trailer relais and the l.bleu/red wire should be for the instrument illumination, radio and more. I think I have a shortcircuit in the l.bleu/red wire because when I "play" with the dimmer the tach. and the oilpressure move a little.