Wiring Issues
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5th Wheeling
Joined: Jun 2018
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Wiring Issues
My 1966 F100 appears to have some sketchy wiring issues which I think are due to some grounding issues. I am not electrical savvy so I need some assistance from you guys with experience how to troubleshoot to see where I have some grounding issues and what tooling or meter to troubleshoot the issues before I break down and install a new harness. Any and all assistance will be appreciated. Also not sure how many grounds i should have.
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5th Wheeling
Joined: Jun 2018
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The front headlights work fine but in the rear I have only one brake light working and when i turn on the signal lights no matter the direction only the right turn signal works whether I turn right or left. The fuel gauge works intermittently so allot of the issues are associated with the rear harness. I just want to be able to check for a potential bad ground I am just unsure how to troubleshoot for a bad ground. I've never done this before but I want to lean on the knowledge of others. Any assistance would be appreciated.
Lead Gopher
Joined: Aug 2012
Posts: 10,021
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From: Seattle
The rear lights are grounded to the bed itself through the housing. The bed is grounded to the frame and the frame is the backbone of the ground plane.
You can take a multi-meter on the ohms or continuity setting to see if there is continuity and a very low ohms reading between
1. Battery negative terminal and Frame
2. Frame and Bed
3. Bed and Housing
A test light can also work but it can be tougher to see if the light is brighter or dimmer than it is to look at the meter and read the ohms.
Here's some other info on another way to do it.
https://www.ford-trucks.com/forums/1...ght-issue.html
Chad
You can take a multi-meter on the ohms or continuity setting to see if there is continuity and a very low ohms reading between
1. Battery negative terminal and Frame
2. Frame and Bed
3. Bed and Housing
A test light can also work but it can be tougher to see if the light is brighter or dimmer than it is to look at the meter and read the ohms.
Here's some other info on another way to do it.
https://www.ford-trucks.com/forums/1...ght-issue.html
Chad
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
As a practical matter the battery cables, ground cables, solenoid to starter, block to firewall and frame, etc, are likely originals (or even just old) they should be replaced, there's no point in trying to test them. Ohms or continuity won't tell you anything anyway.
Now you could measure voltage drop while the circuit is energized, under load. And... they will fail. Go to your local tractor supply store and have them make up a set of heavy gauge cables. Trust Me.
The bullet connectors like in the pic, block connectors through the firewall, are another trouble spot. A wire brush and kerosene will clean them up nice and shiny. Anywhere there is a connector, a ground point, even the fuses in the fuse block on your truck, is going to be suspect 50+ years later.
Now you could measure voltage drop while the circuit is energized, under load. And... they will fail. Go to your local tractor supply store and have them make up a set of heavy gauge cables. Trust Me.
The bullet connectors like in the pic, block connectors through the firewall, are another trouble spot. A wire brush and kerosene will clean them up nice and shiny. Anywhere there is a connector, a ground point, even the fuses in the fuse block on your truck, is going to be suspect 50+ years later.
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5th Wheeling
Joined: Jun 2018
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Ted,, do you think that I should replace the wiring harness and when you say get Tractor Supply to make up some cables are you talking about welding lead and if so what gauge wire would you recommend. I appreciate your in put
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Mountain Pass
Joined: Oct 2016
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I have been having good luck with soda blasting my connectors male and female and then blowing them out with a air hose I used small lead maybe 3/8 od crimped and soldered heat shrieked for my ground wires maybe a little kill but works
mike
mike
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Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
Originally Posted by 66f100restoration
Ted,, do you think that I should replace the wiring harness and when you say get Tractor Supply to make up some cables are you talking about welding lead and if so what gauge wire would you recommend. I appreciate your in put
1 gauge should be enough, I had a battery cable guy on eBay make up a complete set of 2/0 "double ought" size for about $30 delivered. Way overkill, but I don't ever have to worry about voltage drop.
Run the main neg cable directly to the block, or maybe a bolt on the starter. Another to the frame. Grind down to bright shiny metal at these connection points and tighten securely, coat with vaseline or NO-OX, good grounds and connections solve a WHOLE BUNCH of stuff.
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5th Wheeling
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OK today I've spent all afternoon going under and looking at any thing that I could the only ground I found is the ground going to the motor can someone tell me how many places the truck should be grounded. I know that the block should be grounded to the frame I think but if I am wrong let me know. To ground the block to the frame how do I do that and where should the rear wiring harness be grounded at. Thanks for any help/
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
Most people run the negative battery cable directly to the block, or a bolt on the starter.
Then another cable from the block to the frame. Finally a cable from the block to the firewall. Those are the "Big Three" and they are all important. Missing or loose cables can cause brake lines or throttle cables to glow red hot when starting. The starter wants about 200 amps and it's going to get it one way or another. Make sure the starter relay or solenoid itself has a clean connection ground too.
Then another cable from the block to the frame. Finally a cable from the block to the firewall. Those are the "Big Three" and they are all important. Missing or loose cables can cause brake lines or throttle cables to glow red hot when starting. The starter wants about 200 amps and it's going to get it one way or another. Make sure the starter relay or solenoid itself has a clean connection ground too.
Logistics Pro
Joined: May 2015
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From: Tri Cities, TN
Might be a good time to invest in one of these. https://www.ebay.com/itm/1966-Ford-T...sAAOSwBLlVWhgx
Junior User
Joined: Nov 2017
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I had to put new tail lights on my '63 and until I ground both lights to the frame nothing would work right.Just bolting the lights to the bed didn't cut it.The cab was not grounded either.Maybe rust from sitting out in that field or who knows.Anyway,I did replace the turn signal switch as well(at great cost).Seems the 4x4 turn signal switch is different. The turn signal switch is almost like the CPU on newer cars,almost all the important (for driving on the street)wiring goes through it and if the contacts are worn out you will have problems. Good luck!
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