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

Headlight issue

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Old Jul 8, 2015 | 05:52 PM
  #1  
bobs 80 f250's Avatar
bobs 80 f250
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Headlight issue

Just put my 80 F-250 back together. Now I have an issue when I turn the headlights on. Parking and side markers are ok except when I turn on headlights. Just the driver side lights(parking,side marker,and headlight) dim and the turn signal indicator comes on. I assume the indicator is coming on because a back feed. I checked the ground on the fender, but I would expect the lights would be dim all the time. Looking for suggestions and help. I don't have a detailed schematic, except for the one in the Haynes manual I have.
 
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Old Jul 8, 2015 | 06:50 PM
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Just put it back together...what, exactly, did you take apart for this problem to transpire?
 
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Old Jul 8, 2015 | 07:48 PM
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Complete truck. Rebuilt motor, repaied fenders and rad support. I did change to a hei distributor but kept all wiring intact. I thinking a broken wire in harness for headlights.
 
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Old Jul 8, 2015 | 08:16 PM
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If fresh paint ... check for proper grounding . Paint does not ground well .
 
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Old Jul 8, 2015 | 08:16 PM
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Check your fuses. I did the same to my F100. Rebuilt engine and put the front end back together. The headlights were dim and the turn signals would come on with the brake. Turns out I had a fuse out. I think it was a 15 amp one towardd the bottom. Don't know how it was connected but it fixed it.
 
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Old Jul 8, 2015 | 08:38 PM
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Only drivers side is affected. Passenger side is good. Only happens when I turn on headlights. Looking at schematic, the high beam switch is in line, so I'm going to look at that. But tomorrow is another day!!!
 
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Old Jul 9, 2015 | 08:31 AM
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As JWC3 said, I think it is a ground problem.
 
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Old Jul 9, 2015 | 12:37 PM
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Originally Posted by bobs 80 f250
Only drivers side is affected. Passenger side is good. Only happens when I turn on headlights. Looking at schematic, the high beam switch is in line, so I'm going to look at that. But tomorrow is another day!!!
All the switches are common to both sides of the truck correct?
 
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Old Jul 9, 2015 | 01:29 PM
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Originally Posted by Franklin2
All the switches are common to both sides of the truck correct?
Yes, but the grounds are for each side. A bad ground could let the turn signal/parking light ground through the headlight - until the headlight is turned on. And since the fender grounds though it's bolts to the cab, just ensuring the light's ground is well-connected to the fender isn't enough.
 
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Old Jul 9, 2015 | 03:36 PM
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Just for the sake of it, check the dimmer on the floor to be sure the connection is good and it is grounded well. Maybe some rust in that area if not always in SC. Does not sound like it, but easy to check.
 
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Old Jul 9, 2015 | 03:53 PM
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I concur that it is a bad ground or several with the new paint
and reassembly. Clean them all up and don't be afraid to
ad several more where ever you can. Ya just cant have to
many grounds.
 
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Old Jul 9, 2015 | 04:49 PM
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Originally Posted by bcamill
Just for the sake of it, check the dimmer on the floor to be sure the connection is good and it is grounded well. Maybe some rust in that area if not always in SC. Does not sound like it, but easy to check.
There is no ground on that switch.
 
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Old Jul 9, 2015 | 10:48 PM
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I talked to a couple of the mechanics at work today, they all said it sounded like a grounding issue. Unfortunately I didn't get home until late and wasn't able to work on truck. Off tomorrow so I'm installing replacement sockets for the headlights cause they're old. And I'll be adding new grounds and will be sure to clean area where ground goes onto fender. I'll let you all know the outcome!!!!
 
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Old Jul 10, 2015 | 07:23 AM
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Don't forget where the fender bolts to the cab.
 
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Old Jul 10, 2015 | 09:42 AM
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I can see the light!!!!!! Thanks to everyone on their input. It was a bad ground. Cleaned off a spot under the old grond ,new connector and new wire and POW! The lights work.
 
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