Need help with wiring problem
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Joined: Jul 2011
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Need help with wiring problem
Hello, I have a 1966 F-100 SW 4X4 with a 390 and 4spd on the floor. I recently got everything back together and checked all the lights, ect. . .
Everything worked except the ALT light stayed on. I found a yellow wire that was melted down in the harness and what was left of a yellow wire at the voltage regulator. I never could figure out how to get it to work correctly and the harness has been butchered over the years before I got the truck, so I just disconnected the bulb for the ALT light.
When I was almost finished, I noticed the dome light was flickering so I checked everything and found that some of the butt splice connectors were loose, so I took everything apart and started from scratch and this time I soldered the connectors. After I was done I started testing everything, and found a strange problem. When I pull the headlight switch out half way, I have parking lights front and rear. When I pull it out all the way, not only do I NOT have headlights, but the front parking lights go out.
Since EVERYTHING was working except the ALT light before, I can't figure out what the problem could be. I bought a new headlight switch and replaced it, but it didn't change anything. This truck does not have a fuse for the headlights that I can find, and all the fuses test good.
Does anyone have any idea what the problem could be? Also, I was hoping someone might have a wiring diagram for the 1966 F-100 on PDf that I could get a copy of. ??
Any help would be greatly appreciated.
Thanks, Eric
Everything worked except the ALT light stayed on. I found a yellow wire that was melted down in the harness and what was left of a yellow wire at the voltage regulator. I never could figure out how to get it to work correctly and the harness has been butchered over the years before I got the truck, so I just disconnected the bulb for the ALT light.
When I was almost finished, I noticed the dome light was flickering so I checked everything and found that some of the butt splice connectors were loose, so I took everything apart and started from scratch and this time I soldered the connectors. After I was done I started testing everything, and found a strange problem. When I pull the headlight switch out half way, I have parking lights front and rear. When I pull it out all the way, not only do I NOT have headlights, but the front parking lights go out.
Since EVERYTHING was working except the ALT light before, I can't figure out what the problem could be. I bought a new headlight switch and replaced it, but it didn't change anything. This truck does not have a fuse for the headlights that I can find, and all the fuses test good.
Does anyone have any idea what the problem could be? Also, I was hoping someone might have a wiring diagram for the 1966 F-100 on PDf that I could get a copy of. ??
Any help would be greatly appreciated.
Thanks, Eric
Junior User
Joined: Jul 2010
Posts: 69
Likes: 1
From: Wrightsville, PA
Wish I could help you with your question. I will tell you not to be concerned regarding the parking lights. My front parking lights go out when the headlight switch is pulled out all the way -that's normal for the era.
Marty
Marty
Elder User
Joined: Aug 2007
Posts: 516
Likes: 8
From: Milwaukie, Oregon
Sounds like you might have a ground problem somewhere. Loose or rusty grounds can do some strange stuff believe me. As for the wiring diagrams, I can uplaod some pics of my diagram book once my wife gets home and shows me where the camera is. I dont know if it will do much good with your harness your describing, but its worth a shot. I'd find the ground wire for the parking and headlamps and ohms test it to a good ground and see what you got. Should be .5 ohms or less.
Im thinking you found the right guy to help you. I just redid my entire truck wiring with a few modifications. I installed a one wire alternator but the scematics i have are for your system it should all be the same. if only my wife were home...
Im thinking you found the right guy to help you. I just redid my entire truck wiring with a few modifications. I installed a one wire alternator but the scematics i have are for your system it should all be the same. if only my wife were home...
Junior User
Joined: Jun 2003
Posts: 67
Likes: 0
From: Centralia, WA
The voltage regulator controls the ALT light. The current passing through the light's circuit powers the alternator if it is not spinning fast enough to generate it's own power to activate the field. Once the alternator starts operating correctly on it's own, it no longer needs the power from that circuit and the light goes out. Generally, if the light is on then the alternator is not working. Could be a wiring problem between the regulator and alternator, or a faulty alternator, or a faulty regulator.
As for the front marker lights going out when the headlights are turned on, that's the way the switch is designed and is normal for these beasts. When I rewired my truck I changed it so they stay on with the headlights, but that was my choice.
As for the front marker lights going out when the headlights are turned on, that's the way the switch is designed and is normal for these beasts. When I rewired my truck I changed it so they stay on with the headlights, but that was my choice.
Senior User
Joined: Jan 2011
Posts: 123
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From: ?whr down the crazy river
Stoplight switch
It sounds like someone has added a second stop light (brake) switch for one thing, the original was the 2 wires on the master cylinder, brake fluid pressure = stop light on, and the newer style mounted by the brake pedal. 1967>
I read the other post as well and there could have been a power supply for a radio or something like that added, with the red wire dangling?
The original stop light switch to the master cylinder is tied into the flasher, so the wires are disconnected and the new switch on the pedal should be making it light?
If you search for electrical problems related to this like the one below and also for the light switch, there are a lot of previous posts that will help you.
https://www.ford-trucks.com/forums/1...some-help.html
This shows wire colors anyhow
Basic 66 F Model schematic
http://www.justanswer.com/uploads/se...ng_diagram.pdf
I read the other post as well and there could have been a power supply for a radio or something like that added, with the red wire dangling?
The original stop light switch to the master cylinder is tied into the flasher, so the wires are disconnected and the new switch on the pedal should be making it light?
If you search for electrical problems related to this like the one below and also for the light switch, there are a lot of previous posts that will help you.
https://www.ford-trucks.com/forums/1...some-help.html
This shows wire colors anyhow
Basic 66 F Model schematic
http://www.justanswer.com/uploads/se...ng_diagram.pdf
