Wiring Under Dash - Found Broken Wire, Where Does It Go?
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From: Story City, Iowa
Wiring Under Dash - Found Broken Wire, Where Does It Go?
I was working on my '74 F100 this weekend and I was replacing the Headlight and Wiper switches. While doing this I noticed a Black wire with a Blue stripe that had wore down and broke off. I tested the wire for current and it was dead. So I clipped the bad portion off and taped it up until I can figure out what it is for.
The wire comes out of a junction that is on the left side of the dash, between the headlight/wiper switch area and the gauge cluster. It was about 18"-24" lg. (if memory serves me right) before it was broken. There are many things in the truck that don't work, so it's kind of hard to tell what is from.
I tried to take a picture of the the area and the wiring harness that it was connected to, but my camera didn't want to focus on the right stuff, and I needed to put the dash back together for the week, so it's sealed up again.
The wire comes out of a junction that is on the left side of the dash, between the headlight/wiper switch area and the gauge cluster. It was about 18"-24" lg. (if memory serves me right) before it was broken. There are many things in the truck that don't work, so it's kind of hard to tell what is from.
I tried to take a picture of the the area and the wiring harness that it was connected to, but my camera didn't want to focus on the right stuff, and I needed to put the dash back together for the week, so it's sealed up again.
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From: Williamson, NY
When you tested it for current did you do it in all ignition positions? If it did not have current in any ignition positions it could be a ground wire. You could try and connect it to ground and see if some of your non-functioning systems start to work again. It could also be the the current for this wire was coming from the other end where it broke off from. You need to look for where it broke off from, if you can't see a similar broken wire it may have come out of a connector. I have my 77 F150 dash removed right now and all the wires are just hanging there, so I will look and see if I can find a similar wire in that location. When you say the wire came out of a "junction" on the left side of the dash, are you talking about a hard connector or just a taped up bundle of wires?
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From: Story City, Iowa
I did try it in all ignition postitions. Tried it with the doors open, to see if it was the dome light wire or similar, and nothing. But the dome light is a little worse for ware, and the buttons in the doors are shot too. And accourding to the previsous owner, they haven't worked for years.
I didn't try the wire through my ohm meter to see if it was a ground, only to see if there was any current.
I didn't have a chance to pull the gauges out to see if it came from there, but with that said, all the gauge lights work, the temp. gauge works, the radio works and heater works and all exterior lights work to my knowledge. The broken wires are pretty well corroded so it's an old break.
Things that don't work, gas gauge, amp gauge, dome light, and light in radio (if it had one, original AM).
I also don't know if the cigar lighter works. The lighter is broke off inside the housing and I haven't had the chance yet to pull it apart.
When I say it came from a junction, it is a factory wiring harness (hard connector, not a crimped together mess). If I remember right, I think some of the wires coming from this harness go to either the head light or wiper switch, but I can't fully remember now.
I didn't try the wire through my ohm meter to see if it was a ground, only to see if there was any current.
I didn't have a chance to pull the gauges out to see if it came from there, but with that said, all the gauge lights work, the temp. gauge works, the radio works and heater works and all exterior lights work to my knowledge. The broken wires are pretty well corroded so it's an old break.
Things that don't work, gas gauge, amp gauge, dome light, and light in radio (if it had one, original AM).
I also don't know if the cigar lighter works. The lighter is broke off inside the housing and I haven't had the chance yet to pull it apart.
When I say it came from a junction, it is a factory wiring harness (hard connector, not a crimped together mess). If I remember right, I think some of the wires coming from this harness go to either the head light or wiper switch, but I can't fully remember now.
MSEE
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From: Austin, TX
I believe black with blue stripe is the power to the dome light. It is downstream of the door jamb switches. Has power when the doors are open, off when the doors are shut. If you never see power on this wire even with at least one door open, the door jamb switches could be bad. They take a lot of abuse and it's common to have to replace the originals on an old truck.
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From: Story City, Iowa
FMC400, that makes sense, the door jamb switches are shot and next on the list to get replaced. If this wire is for the dome light, where does it go? Or atleast point me in the right direction. The wire is long enough to make it 1/2 way across the dash, so there are alot of places it end.
I'll do a search for dome light wiring diagrahm, unless someone has one avalible.
I'll do a search for dome light wiring diagrahm, unless someone has one avalible.
MSEE
Joined: Apr 2004
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From: Austin, TX
If memory serves me correctly, I *think* it starts from the behind the dash, and goes from the driver's side up through the driver's side windshield pillar, then makes its way across the roof to the dome light. I could be wrong though. Might have to do some poking around. I do know, however, that it goes across the dash, since either the driver's side or passenger's side switch can turn the light on so they are wired together.
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From: Story City, Iowa
If my truck has never had roof lights will that wire still be there? Also, there is no power at the wire with the lights on, turn signals, or 4 way flashers.
The dome light idea makes sense. I searched for a wiring diagrahm that had the dome light in it, and didn't find any. So if any one has one please post.
I need to get a new dome light and door switches ordered, since the switches are shot and the dome light housing looks like crap and the cover is cracked.
Thanks for the help.
The dome light idea makes sense. I searched for a wiring diagrahm that had the dome light in it, and didn't find any. So if any one has one please post.
I need to get a new dome light and door switches ordered, since the switches are shot and the dome light housing looks like crap and the cover is cracked.
Thanks for the help.
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MSEE
Joined: Apr 2004
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From: Austin, TX
Originally Posted by OldThumper
it is for hooking up roof lights.
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From: Story City, Iowa
I was just thinking, I never turned the headlight switch so the dome light would come on. I will try that this evening. If it is for the dome light then that should send power to the wire.
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From: Williamson, NY
I looked at the wiring on my 77 F150 last night and the only black w/ blue striped wires I could find go into the headlight switch. Actually there are two black w/ blue stripe wires going into the headlight switch and they are both going to the same terminal on the right front position of the headlight switch as viewed from the **** end of the switch. Both of these wires lead into main dash wiring harness directly behind the switch, so I can't see where they go from there. I can say for sure that they do not go to the dome light or door jamb switches, since these wires are of a different color, but they must have something to do with truck lighting since they lead to the headlight switch. I would turn the lights on and see if you can find a light that is not working (don't forget the license plate lights and side marker lights).
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From: Story City, Iowa
All the exterior lights work, except for the plate light. This was a farm truck and thus has a Ag type hitch installed. I haven't even seen signs of a plate light wire, but this hasn't been a major concern yet. Otherwise the only lights that do not work are the dome, radio light, and plate light.
And the black w/ blue stripe wire isn't at the headlight switch, it is just beyond in the factory harness that feeds the head light switch. When I replaced the Headlight switch, I double checked all the wires in the connection, and they are all there and tight (as far as I could tell with out running each one).
And the black w/ blue stripe wire isn't at the headlight switch, it is just beyond in the factory harness that feeds the head light switch. When I replaced the Headlight switch, I double checked all the wires in the connection, and they are all there and tight (as far as I could tell with out running each one).
MSEE
Joined: Apr 2004
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From: Austin, TX
Originally Posted by cujo8
I looked at the wiring on my 77 F150 last night and the only black w/ blue striped wires I could find go into the headlight switch. Actually there are two black w/ blue stripe wires going into the headlight switch and they are both going to the same terminal on the right front position of the headlight switch as viewed from the **** end of the switch. Both of these wires lead into main dash wiring harness directly behind the switch, so I can't see where they go from there. I can say for sure that they do not go to the dome light or door jamb switches, since these wires are of a different color, but they must have something to do with truck lighting since they lead to the headlight switch. I would turn the lights on and see if you can find a light that is not working (don't forget the license plate lights and side marker lights).
Plate light = brown wire, part of the running lights circuit. Radio light = blue with red stripe. It is part of the instrumentation lighting, which all use blue with red stripe. The radio gets its power through a 2-prong connector. The yellow with red stripe is the radio power and the blue with red stripe is the lighting. The radio grounds through the mounting bracket.