i have a 91 w250 that i drive everyday to and from base i am have wiring issue i am burning up harneses at the light switch 6in up i have replaced it twice now and all me grounds are good and i cant find any bad connection anyone with advice or an idea why its doing it would be very helpful

 

try replacing the head light switch dont know what it does but i had the same problem and it fixed it

 

The switch could be shorting out inside its self.

 

I have a great set 1st Gen wiring diagrams in a PDF if anyone is interested. Send me your email and I'll fire it out to you.

Dave

 

dave - just pm'd you about the diags

 

Have you replaced any of your factory lights with brighter "better" lights? Adding too much load for the sized wire could be causing your issues. Not to say a bad dimmer couldn't be the culprit.


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I had that problem when hooked to a camper kept burning up head lite switch until i put the running lights on a relay. No more problems

 

i just had the same issue with my truck. ive talked to a few people and i could its kinda common with some of our trucks. even in the 2nd gens. new switches solves the problem.

 

all my lights are stock i have yet to instal my hid lights my switch is new and now a new wiring harness... a good set of wiring diagrams would be helpful since the guy who had it before me loved wire nut and butt connectors so i have 5 hrs of soldering and heat shrinking everything thanks
my email is shane.plummer@navy.mil

 

Mine did the same thing to me. It finally let go and started smoking out of the driver air vent. The switch had shorted inside and was eating harnesses. One thing to keep in mind is when you replace it, make sure nothing rubs against the harness. That was my other problem due the PO's hamfisted approach to electrical stuff. If you're vehicle is IC you're welcome to a copy of my 92 owner's manual. Hit me up with a PM.