Trailer Wiring

[ETM]

Having some Issues with it comes with Wiring up some trailer Light on my Old Truck, Not sure you would have any Ideas. The Wiring on my Tuck is an mess and is cobbled together by an Local Shad Tree guy. So all of the Wires out side of the cab are not the correct colour but I digress. So I've Wired in my Flat 4 plug as best as I can but having some issue with having the Headlights on and using my Brake lights. With my head lights off all is good have turn signals and Brake lights but with my Lights are on I no longer have brake light, Thinking of wiring my running lights to my plate light that I just fixed after this winter with it being broken. Any extra Thoughts or Ideas is gratefully appreciated.

Quote on Quote picture of Rear Bumper.

Sorry moved post over

[Gary Lewis]

I think you have a ground problem. With the headlights off they provide a ground to the brake lights. But with them on they no long provide a ground. I can't tell you where the bad ground is, but I'd bet that you have a ground problem, and probably at the tail lights.

On the early trucks, like yours, there was a ground wired from the light socket to ground on the bed inside the tail light opening. But if your bed isn't grounded well then that could be a problem.

[FuzzFace2]

I think you have a ground problem. With the headlights off they provide a ground to the brake lights. But with them on they no long provide a ground. I can't tell you where the bad ground is, but I'd bet that you have a ground problem, and probably at the tail lights.

On the early trucks, like yours, there was a ground wired from the light socket to ground on the bed inside the tail light opening. But if your bed isn't grounded well then that could be a problem.

I also think it is a ground issue.

As for the truck rear light ground others have posted it is not in the light housing, my parts truck was in the housing.

They say the ground wire picks up both rear lights and goes all the way up front and is tied into other grounds on the firewall behind the radio, so they say.

How did you tie in the flat plug?

You should have a wire to:

The left turn / brake light.

The right turn / brake light.

The running lights - this can tie into either light or the plate light like you posted.

The 4th wire in the plug, think white, is the trailer ground and can go to any clean place on the frame.

Now why this happened after the plug install is beyond me. I think you had this problem before and just seen it now.

https://www.etrailer.com/

Have a lot of good information on how to wire up for a trailer to parts to make this happen.

I have used them for different trailer parts when needed

Dave ----

[Gary Lewis]

I also think it is a ground issue.

As for the truck rear light ground others have posted it is not in the light housing, my parts truck was in the housing.

They say the ground wire picks up both rear lights and goes all the way up front and is tied into other grounds on the firewall behind the radio, so they say.

How did you tie in the flat plug?

You should have a wire to:

The left turn / brake light.

The right turn / brake light.

The running lights - this can tie into either light or the plate light like you posted.

The 4th wire in the plug, think white, is the trailer ground and can go to any clean place on the frame.

Now why this happened after the plug install is beyond me. I think you had this problem before and just seen it now.

https://www.etrailer.com/

Have a lot of good information on how to wire up for a trailer to parts to make this happen.

I have used them for different trailer parts when needed

Dave ----

Dave - I'll have to check when the change was made in the grounds, but I'm pretty sure it was for '85. Prior to that there was a ground wire in the tail light opening. After that the grounds were collected into one wire that went all the way back into the cab.

[ETM]

I also think it is a ground issue.

As for the truck rear light ground others have posted it is not in the light housing, my parts truck was in the housing.

They say the ground wire picks up both rear lights and goes all the way up front and is tied into other grounds on the firewall behind the radio, so they say.

How did you tie in the flat plug?

You should have a wire to:

The left turn / brake light.

The right turn / brake light.

The running lights - this can tie into either light or the plate light like you posted.

The 4th wire in the plug, think white, is the trailer ground and can go to any clean place on the frame.

Now why this happened after the plug install is beyond me. I think you had this problem before and just seen it now.

https://www.etrailer.com/

Have a lot of good information on how to wire up for a trailer to parts to make this happen.

I have used them for different trailer parts when needed

Dave ----

So it is wired into the

Left Brake and Turn

Right Brake and Turn

Then the Running is wired into the Right Running light

^ Thinking of changing this to the plate light and see if this helps.

Grounded to the bed but may change it to the Frame

Been raining non stop.

[Steve83]

This gives the old Ford colors, the revised Ford colors, the later standard vehicle colors, the standard trailer colors, and the standard trailer connector colors:

https://supermotors.net/getfile/822003/thumbnail/trailerconnectors.jpg

If the headlights affect the taillights, it's likely because the taillights are not grounded. The easiest way to fix them is to run their black wire all the way to the engine block, frame, or body ground (so it's in contact with the big negative cable).

[FuzzFace2]

I also think it is a ground issue.

As for the truck rear light ground others have posted it is not in the light housing, my parts truck was in the housing.

They say the ground wire picks up both rear lights and goes all the way up front and is tied into other grounds on the firewall behind the radio, so they say.

How did you tie in the flat plug?

You should have a wire to:

The left turn / brake light.

The right turn / brake light.

The running lights - this can tie into either light or the plate light like you posted.

The 4th wire in the plug, think white, is the trailer ground and can go to any clean place on the frame.

Now why this happened after the plug install is beyond me. I think you had this problem before and just seen it now.

https://www.etrailer.com/

Have a lot of good information on how to wire up for a trailer to parts to make this happen.

I have used them for different trailer parts when needed

Dave ----

So it is wired into the

Left Brake and Turn

Right Brake and Turn

Then the Running is wired into the Right Running light

^ Thinking of changing this to the plate light and see if this helps.

Grounded to the bed but may change it to the Frame

Been raining non stop.

Sorry not getting back sooner.

Yep that is how it should be done.

I cant see picking up running lights from the plate light would help the issue but if it makes you happy then go for it.

BTW there is a Tee trailer harness, Etrailer or others, that you unplug the trucks tail lights from the rear harness plug in the trailer harness to the rear harness and the tail lights to the trailer harness.

1 of my trucks came with one and will be using it on mine when I get that far.

Dave ----

[ETM]

BTW there is a Tee trailer harness, Etrailer or others, that you unplug the trucks tail lights from the rear harness plug in the trailer harness to the rear harness and the tail lights to the trailer harness.

1 of my trucks came with one and will be using it on mine when I get that far.

Dave ----

Sorry about the Delay, The Wiring in this truck is an mess other then the Interior Was an real Shad Tree Job, it works but lots of wires just taped together, I like to Solder and shrink tube it. Will have to Go over it later. Tested will an Test Light Seems to work fine will new more when the U-Haul Trailer is Hitched up. Thanks for all of the help.

 

[81f100custom]

BTW there is a Tee trailer harness, Etrailer or others, that you unplug the trucks tail lights from the rear harness plug in the trailer harness to the rear harness and the tail lights to the trailer harness.

1 of my trucks came with one and will be using it on mine when I get that far.

Dave ----

Sorry about the Delay, The Wiring in this truck is an mess other then the Interior Was an real Shad Tree Job, it works but lots of wires just taped together, I like to Solder and shrink tube it. Will have to Go over it later. Tested will an Test Light Seems to work fine will new more when the U-Haul Trailer is Hitched up. Thanks for all of the help.

This is what I have on mine. I believe this is what FuzzFace2 was also referring to. Its plug and play if you still have that much of the harness intact.

https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Ford/F-100,+F-150,+F-250,+F-350/1981/HM40115.html?vehicleID=19811171990

[FuzzFace2]

This is what I have on mine. I believe this is what FuzzFace2 was also referring to. Its plug and play if you still have that much of the harness intact.

https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Ford/F-100,+F-150,+F-250,+F-350/1981/HM40115.html?vehicleID=19811171990

Yes that is what I was talking about.

Now if his wiring is that bad back there he may want to try and find a good one in the junk yard.

He would need to match his truck if it has duel tanks so the harness would have the sender and tank switching valve wires. If he has electric pumps that would be another reason to make sure the new harness has them.

Now if this harness down the side of the frame rail is still good but it is the tail light harness is the bad part then all he would need is that tail light harness and it plugs into that frame rail harness.

Then when he does the tail light harness swap he could plug in that trailer harness.

Dave ----