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My 1991 F250 7.3 diesel keeps frying the fuses for the dash light and tail lights. It's been an issue for over a week now. I replaced the headlight switch which had a burned out area (melted). The problem is that my 15 amp Number 4 fuse is burning out frequently. Some times it will be OK while in park but fries when in gear and moving. Other times it fries as soon as the lights come on. I have rewired my rear lights and took out my trailer wiring harness and plug. I have cleaned up the rear Ground above the spair tire. I replace the trailer wire relay under the hood. I have had this in the 2 different shops this week and they have not found it .
I plan on starting on the front of the truck tommorow and look at the front running lights. I really need some help with this.
1991 F250 7.3 diesel. WhileI was trying to remove the instrument panel to check the wiring I was palying with the headlight (dimmer) switch. The 15 amp #4 fuse for the dash lights was pulled at the time due to it blowing every time I turned the lgihts on. As I pulled the switch out I could hear the headlight switch click and I slowly pushed the switch in again. My dash lights came on??? How can they come on with the fuse out? The dimmer switch looks corroded and the tong that had been attached to the t/wh wire that had burned out on the Headlight switch looked scortched when I pulled the connection apart again.
I reconnected the switches again and found I could get the dash lights on if I played with the pull switch. I'm not sure how it does this with the fuse out?
I reconnected the switches again and found I could get the dash lights on if I played with the pull switch. I'm not sure how it does this with the fuse out?
The headlight switch has several sections to it, fed from different power sources. When you put the switch in an unusual position, the contacts in the switch are bridging the gap between on circuit and another. So they are getting power from the wrong source when the switch is in an odd position.
As far as your fuse blowing problem, you are doing the right thing by checking all the wiring. You might want to look the harness over, and check for plugs. If you find wiring harness plugs in strategic locations, you may be able to unplug whole sections of the wiring to see if the problem is there or not. The brown wire is the culprit, and as you know already it is spread through-out the truck.
I have been trying to trace the brown wire under the dash but I am having a hard time taking the dash or instrument panel off to get at the wires. Someone told me that they had the brown wire melt and fuse to a ground wire under the dash and I was going to try to look at that. Four full days of troubleshooting so far....
My relay for the trailer lights under the Hood seems to have nbeen the issue. I bought a new one and it still was blowing fuses. Whn I unhooked the relay the problem was gone. I had two 7 pin trailer connectors hooked up, one for camper and one for boat. I have taken the boat one off and unhooked the trailer ones from my rear lights.
I just finished the Brighter Lights Relay project and I must say it sure brightened my lights up conciderably.