Can NOT get trailer lights to work

[Bearsixty7]

Might wanna pick up a 7 pin rv plug from the local parts store that is labeled for color and try it out.

You'll find the diagram you posted is incorrect. Functions labeled in your diagram are correct. The colors are wrong though.

Not sure on the vehicle side. All I test for is function there when diagnosing a trailer issue.

On the trailer side, blue and white are correct. Yellow is labeled as the center plug for aux power. Black is back up lights, red is right turn, brown is left turn, green is right turn.

I haven't seen a replacement 7 pin rv plug thats been labeled for function in about 6 years. They've come labeled for color and wire up as I stated above.

I just replaced two of those plugs today on equipment at work.

I take a plug apart Monday and post a picture.

Oh, you said "There are wire color changes going from a four flat to a 7 pin rv plug that is standard on most trucks.
The yellow wire on a 4 flat is left turn, green is right turn, brown is parking lights. Once you get up to the 7 pin, yellow is aux power, brown is right turn, green is parking lights, red is actually for left turn."

So I thought you meant the trucks were wired differently.
As far as I know most trucks have used this color scheme for years and that is what I was referring to.
Trailers, well who knows, You would think that trailer manufacturers would follow suit (and some day they will) but we all probably have encountered trailers that were wired weird and a nightmare to correct.

 

[pmsmechanic]

but we all probably have encountered trailers that were wired weird and a nightmare to correct.

I once worked on a stock trailer that had the wiring inside in one of the frame tubes running front to rear. Inside the tube was a splice and a wiring color change at the splice. Grrrrr!

 

[tstex]

Here's an out of the box question for those that have been following this thread, but w one note prior to ques. It's apparent on the F-150 and other trucks that have the trailer receptacle so low, has been hit, pelted and water soaked under flooded conditions. That's probably the case w mine bc we sometimes get 5-10" rains and the streets are flooded.

With that thought in mind, has anyone ever tried relocating the receptacle to higher up on the bumper, like near the license plate lights? At least it would not get smashed or hit w water as much. Not sure about rain when parked outside, how that might impact the plug. Since the bumper is basically hard plastic in that area, I could buy another bracket and install...then it's plug'n'play. Thoughts ??

 

[Norm W]

Being color crippled everything is done with a test light. I don't care what color the wires are. Many times I think the manufacturers use what ever color they have handy. If the wires are live when the appropriate light is turned on it is marked with numbered tape. The usual problem with trailers is bad grounds. I always run a separate ground wire.

 

[dodge man]

Not a great picture, it of the lights I added to a bike rack, but if you look closely you can see the trailer lights plug in to the left of the license plate. It’s that way from the factory.

 

[RandyT]

Being color crippled everything is done with a test light. I don't care what color the wires are. Many times I think the manufacturers use what ever color they have handy. If the wires are live when the appropriate light is turned on it is marked with numbered tape. The usual problem with trailers is bad grounds. I always run a separate ground wire.

Agree on the separate ground. Every trailer that I have wired I run a separate ground wire and connect to each light. and then connect everything to the trailer plug. I don't use the trailer frame to ground anything on the trailer.

 

[Dftodd]

Here's an out of the box question for those that have been following this thread, but w one note prior to ques. It's apparent on the F-150 and other trucks that have the trailer receptacle so low, has been hit, pelted and water soaked under flooded conditions. That's probably the case w mine bc we sometimes get 5-10" rains and the streets are flooded.

With that thought in mind, has anyone ever tried relocating the receptacle to higher up on the bumper, like near the license plate lights? At least it would not get smashed or hit w water as much. Not sure about rain when parked outside, how that might impact the plug. Since the bumper is basically hard plastic in that area, I could buy another bracket and install...then it's plug'n'play. Thoughts ??

Mine is mounted stock next to the tag on my Sierra so it's protected.

I'm on my second replacement on my service truck. First time it shorted out in a quarry. Had to go through 3'ft of water to get to the equipment I was working on.

Second time was last week. There was a frame recall on the truck. They had to pull the bed and crane to add support rails behind the cab.

Tech snapped a couple pins in the quick connect when he hooked it back up.

I saved the old one so I can show the service manager at the dealership. His shop foreman needs to get more pictures so they can get paid for the recall. So I'm gonna swing by Monday. I'll bring it to there attention then.

 

[Dftodd]

Agree on the separate ground. Every trailer that I have wired I run a separate ground wire and connect to each light. and then connect everything to the trailer plug. I don't use the trailer frame to ground anything on the trailer.

Boss had a small tilt trailer that he couldn't get the lights working on. He replaced the ground wire and hooked it to the tongue. Cleaned the connection for the ground on the lights.

I pointed out that he needed to run a jumper wire from where he hooked the ground to the tongue, to the frame where his lights attached he didn't take unto account for the loss of connection where it pivots.

 

[RandyT]

Boss had a small tilt trailer that he couldn't get the lights working on. He replaced the ground wire and hooked it to the tongue. Cleaned the connection for the ground on the lights.

I pointed out that he needed to run a jumper wire from where he hooked the ground to the tongue, to the frame where his lights attached he didn't take unto account for the loss of connection where it pivots.

Sounds like another case of somebody thinking that the trailer is supposed to be grounded through the trailer ball back to the tow vehicle instead of through the trailer wiring harness back to the wiring harness on the tow vehicle and then connected to the vehicle frame or negative battery terminal.

 

[Dftodd]

Sounds like another case of somebody thinking that the trailer is supposed to be grounded through the trailer ball back to the tow vehicle instead of through the trailer wiring harness back to the wiring harness on the tow vehicle and then connected to the vehicle frame or negative battery terminal.

He actually ran a ground to the tongue. What got him was his lights were mounted to the portion of the trailer that pivoted. he didn't take that into account.