Help with a Bad Short
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Junior User
Joined: Dec 1999
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From: Hubbard USA
Help with a Bad Short
Was having some trouble with my light switch. The parking lights/dash lights would not stay on unless I wiggled the switch.
Then the parking lights went out altogether. Replaced the switch, and as soon as I turned on the lights, the #4 fuse blew. Checked for obvious problems could not find anything. Took the switch out again, and found that the wiring for the parking lights to and from the switch had the insulation melted off for about 4 inches up the line.
Any suggestions where thing might be going wrong? What could draw some much power that the wire insulations would melt? Does this kind of thing happen on a 1989 F250?
Thanks for amy help.
Dave
Then the parking lights went out altogether. Replaced the switch, and as soon as I turned on the lights, the #4 fuse blew. Checked for obvious problems could not find anything. Took the switch out again, and found that the wiring for the parking lights to and from the switch had the insulation melted off for about 4 inches up the line.
Any suggestions where thing might be going wrong? What could draw some much power that the wire insulations would melt? Does this kind of thing happen on a 1989 F250?
Thanks for amy help.
Dave
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From: Virginia
Ford switches and wiring are notorious for being barely capable of running the factory lighting load. Do you have any extra lights installed on your truck? Did you just buy this truck and the previous owner may have had more lighting installed?
A loose connection at the switch can cause overheating of the plug and the wiring too. The bare melted wire must have got up against something and blew the fuse. You may be ok now with the new switch but the headlight wiring plug may still be bad. Look at it and see if it's melted or the contacts do not look good. If it's in bad shape, you may have this problem again.
A loose connection at the switch can cause overheating of the plug and the wiring too. The bare melted wire must have got up against something and blew the fuse. You may be ok now with the new switch but the headlight wiring plug may still be bad. Look at it and see if it's melted or the contacts do not look good. If it's in bad shape, you may have this problem again.
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Junior User
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From: Hubbard USA
No, there are no other lights installed.
As I inspected the switch plug itself, I noticed it was beginning to melt around the parking light contacts.
It looks to me, like the whole bundle of wires from the switch need to be replaced. Does that sound right? And if so, how difficult is it to get to the wiring? does the dash need to be removed?
One more question, could the switch itself have cause this problem? or should I look for another short elsewhere?
Thanks
As I inspected the switch plug itself, I noticed it was beginning to melt around the parking light contacts.
It looks to me, like the whole bundle of wires from the switch need to be replaced. Does that sound right? And if so, how difficult is it to get to the wiring? does the dash need to be removed?
One more question, could the switch itself have cause this problem? or should I look for another short elsewhere?
Thanks
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From: Virginia
Look at the damage. If it concentrated mainly from the switch plug, and lessens the farther away you un-wrap the harness, then I would suspect the plug and it's connections to the switch probably started the whole thing. All the heat from the loose connection ruined the switch and the wiring right around the plug.
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Help
Just looking for help, I have a 1986 F150 302ci EFI, the same thing just started happening. The running lights will not turn off, I have replaced the headlight switch and removed all fuses from the inside fuse block. They will not turn off!
Please Help
Please Help
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Joined: Jan 2001
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From: Virginia
Originally Posted by ckdye
Just looking for help, I have a 1986 F150 302ci EFI, the same thing just started happening. The running lights will not turn off, I have replaced the headlight switch and removed all fuses from the inside fuse block. They will not turn off!
Please Help
Please Help
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New User
Joined: Jan 2006
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same deal
Hey
I've got an aircraft refueler built on a f350, factory built as such. I'm haveing the exact same problem, the #4 fuse continues to blow every time. My problem is identical to the original post, except I do have one additional light installed simply to read a gallon flow meter. It doesn't draw much power, but I can't see why it would be too much to blow the fuse. Now because of all the additional mechanical add-ons to the truck it makes it almost impossible to trace wiring from front to back, so finding the particualr spot causing the short probably won't happen. Any suggestions?
Thanks
I've got an aircraft refueler built on a f350, factory built as such. I'm haveing the exact same problem, the #4 fuse continues to blow every time. My problem is identical to the original post, except I do have one additional light installed simply to read a gallon flow meter. It doesn't draw much power, but I can't see why it would be too much to blow the fuse. Now because of all the additional mechanical add-ons to the truck it makes it almost impossible to trace wiring from front to back, so finding the particualr spot causing the short probably won't happen. Any suggestions?
Thanks
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From: Marlboro Mental Hospital.
on my 88, i cut back about 5 inches to get rid of all the bad wire. then i wired in a new switch end, and put a new switch in. then i went into the engine bay, and cut the wire going to the headlights, and wired in relays.the relays get power directly from the battery. the running lights are relay switched also. now the only job the headlight switch has had since 1990 is to trigger the relays.
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From: Virginia
Someone on here said they went to the Ford dealer, and they sell a short pigtail to repair the wiring to the switch and give you a new plug too. With a new switch and a new wiring pigtail this should fix you up if your wiring looks melted near the switch.
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Well, the switch has already been replaced, it works perfectly fine, my problem was a burn on the socket, I cut that wire back and replaced the pin for it. Everything is fine in appearance, yet there is still a short somewhere. I'm tempted to run a lead diretly to the ignition switch, but that is a worst case scenario idea. Any other suggestions?
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From: Virginia
I am going to assume the #4 fuse on your aircraft truck serves the running lights? Let's get that cleared up first.
If it does, and the fuse only blows when you pull the lightswitch, I would follow the wiring harness out of the firewall, and hopefully somewhere along the way you should find some plugs that you can disconnect. The running light circuit is fed with a brown wire. The only hope you have is to unplug some of the harness, so you can at least narrow it down to the front of the vehicle or the rear. This circuit runs over the whole truck. The pickups have a plug in the rear too, if yours still has it.
If it does, and the fuse only blows when you pull the lightswitch, I would follow the wiring harness out of the firewall, and hopefully somewhere along the way you should find some plugs that you can disconnect. The running light circuit is fed with a brown wire. The only hope you have is to unplug some of the harness, so you can at least narrow it down to the front of the vehicle or the rear. This circuit runs over the whole truck. The pickups have a plug in the rear too, if yours still has it.
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