wiring nightmare
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Senior User
Joined: Jan 2006
Posts: 135
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From: northwest Georgia
wiring nightmare
well, the title pretty much explains it. i bought a trailer wiring harness to put on my 85 f150 and thought i'd fix my taillight wires first. The previous owner had hacked them so much they were a jumble of wires. so i cut out all the extra wires and hooked them up the way they were, and they wouldn't work. the taillights would only work when the ignition was on and they go off when you pull the light switch out. the reverse lights only come on when the turn signal is on, and the turn signals act like the hazards are on when either one is on. I really need help since i dont know what to do. The wires are EXACTLY matched up color for color. any help would be greatly appreciated.
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Joined: Sep 2003
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From: Right Next to U
"the taillights would only work when the ignition was on and they go off when you pull the light switch out."
Light switch is shorted or needs replacing.
"the reverse lights only come on when the turn signal is on."
The Reverse lights are wired into the Turn Signal wiring harness. It should be into the reverse light switch.
"and the turn signals act like the hazards are on when either one is on."
Same problem as above. Wrong placement of wiring.
"The wires are EXACTLY matched up color for color. "
The trailer wiring is universal which simply means it will work as long as you trace out the "placement" of the required wiring. Just because the wires are the same color doesn't mean they go into the same wires.... A good multimeter and a wiring diagram is what you need for the model and year of your vehical. Then simply match the correct wires to the placement of what you want it to do.
Light switch is shorted or needs replacing.
"the reverse lights only come on when the turn signal is on."
The Reverse lights are wired into the Turn Signal wiring harness. It should be into the reverse light switch.
"and the turn signals act like the hazards are on when either one is on."
Same problem as above. Wrong placement of wiring.
"The wires are EXACTLY matched up color for color. "
The trailer wiring is universal which simply means it will work as long as you trace out the "placement" of the required wiring. Just because the wires are the same color doesn't mean they go into the same wires.... A good multimeter and a wiring diagram is what you need for the model and year of your vehical. Then simply match the correct wires to the placement of what you want it to do.
Lead Driver
Joined: Oct 1999
Posts: 6,779
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From: Kalispell, MT
Color for color doesn't usually work - Ford varied the stuff so much that each year/model is different.... plus aftermarket is just a guess.
The way I do it - find a partner to pull ***** and push pedals, get a 12V test light and crawl under. Disconnect everything you hooked up and one wire at a time figure what it goes to. It's a time consuming pita, but it's the only reliable way to get it done.
The way I do it - find a partner to pull ***** and push pedals, get a 12V test light and crawl under. Disconnect everything you hooked up and one wire at a time figure what it goes to. It's a time consuming pita, but it's the only reliable way to get it done.
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Joined: Jan 2001
Posts: 56,997
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From: Virginia
Ford always used brown for the taillights. Find that wire first. Do what mtflat said, and put a testlight on the brown, and pull the headlight switch out. If you get the testlight working correctly, then make sure the brown wire is wired correctly to the lights in the rear. It should go to a splice, were it splits up and goes to each taillight, and also to the license plate lights.
The brown wire should go to the dimmer of the two filaments in the rear bulbs. Also make sure the black wire is grounded to a good ground on the frame.
I would get this working first. Then you can move on to the turn/brake wires, and then the back-up wires.
The brown wire should go to the dimmer of the two filaments in the rear bulbs. Also make sure the black wire is grounded to a good ground on the frame.
I would get this working first. Then you can move on to the turn/brake wires, and then the back-up wires.
Senior User
Joined: Jan 2007
Posts: 334
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From: Milltown, NJ
I agree with mtflat & Franklin. I am, by no stretch of the imagination, a wiring pro. I did the rear truck/trailer wiring (4 wire set up) the way they did.
IT ACTUALLY WORKED!!!
Just take your time, do one wire at a time.
Good Luck.
IT ACTUALLY WORKED!!!
Just take your time, do one wire at a time.Good Luck.
New User
Joined: Jan 2008
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Likes: 24
I suspect you have some light grounding issues with your truck.
This is the North American standard wiring.
I did mine to match MY trailer so in the even it was stolen..the lights wouldn't work there for being a target for police to pull it over and a ASK questions.
I also made up some pigtails to fit other plug-in's.
This is the North American standard wiring.
I did mine to match MY trailer so in the even it was stolen..the lights wouldn't work there for being a target for police to pull it over and a ASK questions.
I also made up some pigtails to fit other plug-in's.
Last edited by Mil1ion; Apr 2, 2007 at 03:13 PM.
Thread Starter
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Senior User
Joined: Jan 2006
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From: northwest Georgia
no no no, i didn't even put the harness in yet. the problems i listed are just with the stock wiring. everything worked fine before i started so i know its something i did, but i hooked the wires up exactly like they were before. left turn signal to green/orange, right turn signal to orange/blue, brown to lights, and black/pink to reverse.
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New User
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I would be checking the run of all the wires coming out of the TS switch down along the column and along the frame.
Ford's wiring for everything seems to run through the Turn Signal switch.
As I remember
With key in OFF
Hazard Lights work
Brake Lights work
Marker Lights work w/switch
Headlights work w/switch
With Key In RUN only
T/S's will work
Back-up lights will work w/trans in reverse
Ford's wiring for everything seems to run through the Turn Signal switch.
As I remember
With key in OFF
Hazard Lights work
Brake Lights work
Marker Lights work w/switch
Headlights work w/switch
With Key In RUN only
T/S's will work
Back-up lights will work w/trans in reverse
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Thread Starter
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Senior User
Joined: Jan 2006
Posts: 135
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From: northwest Georgia
the hazards still work ok, the brakes now work when the light switch is off. if the switch is on, they don't work, and the turn signals still both flash no matter which way i put the turn signal switch.
getting there.
getting there.
Thread Starter
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Senior User
Joined: Jan 2006
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From: northwest Georgia
i didn't bother to do that before because they worked fine right before i messed with them, but i will check anyway. the chance that a bulb or socket going out at that same time is too small. are the four wires in that bundle suppose to have 12 volts running to them all the time? i checked with a volt meter and they do, even when they are off.
