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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

wiring issues

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Old May 10, 2023 | 05:26 AM
  #1  
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wiring issues

i bought a 81' f150 3 weeks ago, its been a journey so far with brake issues, power steering and much more. the previous owner swapped the 81 bed with a eddie bauer 96-97 bed, the wiring did not match at all as to be expected. i now have a 86' bed on it with the correct wiring, i have some weird things happening when i brake, use turn signals, turn lights on. ill explain: when you turn the lights on the tail lights do not come on,
when you use the turn signals no matter left or right, they both flash like the hazards are on.
if you turn on the lights and the hazzard switch on the tail lights come on and stay on solid, if you brake the lights go off.
everything is backwards it feels like but its connected properly, what in the world is going on?
i did find a wire behind the fuse box that is melted up a ways (just discovered it early this morning)
its # 4 on the fuse panel. one more twist, when using trailer lights everything almost works perfectly. both tail lights work, so do the blinkers.
im a bit stumped.

 
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Old May 10, 2023 | 07:43 AM
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Dear a bit stumped,

Welcome to the forum. Can't help with what has been modified, but this troubleshooting guide may help by showing how the stock 80-86 system worked:

https://www.ford-trucks.com/forums/1...ing-guide.html

 
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Old May 10, 2023 | 08:51 AM
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It should not matter if the wire colors match or not.
There should be a plug at the left rear corner that the tail light harness plugs into.
I would unplug it and using a test light check what each wire dose. If not right on the truck side it will not be good on the light side.

Also check the grounds in the truck.
Battery to motor, motor to frame and motor to cab as this almost sounds like a ground issue.

BTW how are the lights grounded?
I think there should be a ground wire in the frame rail harness but not 100% sure on that.
How many wires at that plug on the truck side?
Think 4 for lights and 1 for ground makes 5 wires.
Dave ----
 
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Old May 13, 2023 | 12:13 PM
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Old May 13, 2023 | 12:13 PM
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I agree with Dave. Seems like a ground issue.
there are several ground wires between the the light housings and the frame rails depending on the year of the truck.
Grounds should not be overlooked as they are HALF OF THE CIRCUIT
 
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