Insane Electrical Problems
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Lead Driver
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Insane Electrical Problems
I have an electrical train wreck and I don't know why. I doubt anyone can help me but I'm going to ask in case someone has seen something like this before.
I have a '76 highboy , all the electrical was fine. I pulled the engine to rebuild it , cleaned up the engine bay and re taped the harnesses. and removed an old brake controller and replaced a broken turn signal cam. that's all I've done. this is a nice pickup the wiring looks good .
What I have now is a mess. all the side markers work, the tail lights do not. the park lamps do not.
No turn signals work.
With the hazards on the front works the back does not.
The stop lights do not work. but the brake switch does, it's putting out 12v but it's not getting to the inside of the firewall plug.
Is there any logical place to start on this ?
I have a '76 highboy , all the electrical was fine. I pulled the engine to rebuild it , cleaned up the engine bay and re taped the harnesses. and removed an old brake controller and replaced a broken turn signal cam. that's all I've done. this is a nice pickup the wiring looks good .
What I have now is a mess. all the side markers work, the tail lights do not. the park lamps do not.
No turn signals work.
With the hazards on the front works the back does not.
The stop lights do not work. but the brake switch does, it's putting out 12v but it's not getting to the inside of the firewall plug.
Is there any logical place to start on this ?
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Lead Driver
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The engine is still out actually, so I ran the ground to the core support just to check my turn signals and found the other problems. . headlights, radio all of that works fine. I'll run a jumper to the bed though to see. though the side markers do work on it.
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Lead Driver
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I still can't figure how it would keep the stop lights or the tail lights from working but I can't find anything else wrong so I'll see.
Brake switch is definetly sending juice out but it's not getting out of the cab to the firewall plug . I pulled the instrument cluster and everything looks great with the harness. if the turn switch doesn't fix it I'm clueless.
Brake switch is definetly sending juice out but it's not getting out of the cab to the firewall plug . I pulled the instrument cluster and everything looks great with the harness. if the turn switch doesn't fix it I'm clueless.
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New User
Joined: Nov 2018
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From: Seattle, WA
The tail lights would be run through the turn signal switch so that the light can blink when you turn on the indicator.
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Moderator & parts slinger
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Sounds like the ts switch is causing you issues. TS wiring harness replacement. https://www.ford-trucks.com/forums/1...l#post14696830
Elec diagrams start here. https://www.ford-trucks.com/forums/1...l#post14696846
TS plug https://www.ford-trucks.com/forums/s...&postcount=177
TS 101 https://www.ford-trucks.com/forums/1...l#post18338355
Elec diagrams start here. https://www.ford-trucks.com/forums/1...l#post14696846
TS plug https://www.ford-trucks.com/forums/s...&postcount=177
TS 101 https://www.ford-trucks.com/forums/1...l#post18338355
Logistics Pro
Joined: Oct 2006
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From: East Central Ia
Brake lamps run through signal switch, tail lamps and markers run through headlamp switch.
Senior User
Joined: Nov 2015
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From: FL & NY
RE: electrical problems
If all was working prior to cleaning up the underhood area, I would tackle 1 problem at a time.
You say you removes trailer wiring - that may have created an issue with the rear stop & tail lights; start by checking harness connections from front to back.
Spent some time troubleshooting before throwing parts at it. Check the obvious first - harness connections, pinched wires, fuses, grounds, bulbs, etc.
It the side marker lights are working, the tail lights should be working as well, UNLESS there was some add-on wiring done for the trailer harness.
The tail lights DO NOT feed thru the turn signal switch.
The stop light circuit is 12v from fuse panel to the stop light switch then to steering column harness to the turn sig. switch. With the turn sig. sw. in the center position, power should be fed thru the turn sig. sw. then to the 2 wires feeding the left and right rear lamp sockets. At this point, with the key off, both stop lamps should light and the 4 way flashers (front & rear) should work when turned on.
Happy hunting !
You say you removes trailer wiring - that may have created an issue with the rear stop & tail lights; start by checking harness connections from front to back.
Spent some time troubleshooting before throwing parts at it. Check the obvious first - harness connections, pinched wires, fuses, grounds, bulbs, etc.
It the side marker lights are working, the tail lights should be working as well, UNLESS there was some add-on wiring done for the trailer harness.
The tail lights DO NOT feed thru the turn signal switch.
The stop light circuit is 12v from fuse panel to the stop light switch then to steering column harness to the turn sig. switch. With the turn sig. sw. in the center position, power should be fed thru the turn sig. sw. then to the 2 wires feeding the left and right rear lamp sockets. At this point, with the key off, both stop lamps should light and the 4 way flashers (front & rear) should work when turned on.
Happy hunting !
Logistics Pro
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I'm always suspicious of any area where work was done, in cases like this.
My guess is that you have something unplugged under the hood. Could be some connector up by the master cylinder, or maybe it could be because the alternator is disconnected.
When my TS switch went bad, the arm was sagging down. It wasn't sagging enough to make the left side indicator flash, but it was hanging down enough to disengage the "Off" contacts, killing one of my brake lights.
Be suspicious of any area where you've been working, like the TS switch, and any connectors under the hood which you've had anything apart.
My guess is that you have something unplugged under the hood. Could be some connector up by the master cylinder, or maybe it could be because the alternator is disconnected.
When my TS switch went bad, the arm was sagging down. It wasn't sagging enough to make the left side indicator flash, but it was hanging down enough to disengage the "Off" contacts, killing one of my brake lights.
Be suspicious of any area where you've been working, like the TS switch, and any connectors under the hood which you've had anything apart.
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Lead Driver
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I've done a bunch of worked since I tested the lights so there are multiple places for problems.
I will work on the taillights, there was some funky wiring back there it's entirely possible removing the trailer plug did something. my front park lamps don't work either. this makes no sense as I did nothing to the. they do flash on the hazard though.
I did unplug everything under the hood but I've checked and rechecked it. and since my rear side markers work so the rest should I'd think.
I will work on the taillights, there was some funky wiring back there it's entirely possible removing the trailer plug did something. my front park lamps don't work either. this makes no sense as I did nothing to the. they do flash on the hazard though.
I did unplug everything under the hood but I've checked and rechecked it. and since my rear side markers work so the rest should I'd think.