Camper wiring issue - I’m stumped.

[EVOlutionary]

I have a 2005 F250 and a 2021 FR Salem. When I picked up the camper the dealership said my truck trailer tow wiring was bad, as the right turn signal didn’t work on the camper. I verified this with a 7-pin plug tester - right flasher signal was bad. Had the Ford dealership fix it. Now tests fine on the plug tester but the right camper turn signal still does not work.

I hook the truck up to my car hauler and the right turn signal DOES work. So I of course think it’s just a blown bulb on the Salem. But here’s the weird part - when I hook the Salem up to my 2014 Durango - all lights work properly. 😬

What could possibly be causing this?

[Reverse_snowbird]

Got to be the Ford if it works when you hook it up to the Durango and all lights work properly.

[Bama Rambler]

Does your car hauler have LED lights?

It could be the Ford circuit failing when put under load. If possible, I'd hook it to another trailer that has incandescent bulbs and see if it works then.

[EVOlutionary]

Originally Posted by Bama Rambler

Does your car hauler have LED lights?

It could be the Ford circuit failing when put under load. If possible, I'd hook it to another trailer that has incandescent bulbs and see if it works then.

It does indeed. Good idea. I’ll check that out.

[aircommuter]

Originally Posted by EVOlutionary

It does indeed. Good idea. I’ll check that out.

Does it still work at the plug?

[EVOlutionary]

Originally Posted by aircommuter

Does it still work at the plug?

The 7-pin on the truck? I have a plug-in tester and all lights work properly on the tester.

[aircommuter]

Originally Posted by EVOlutionary

The 7-pin on the truck? I have a plug-in tester and all lights work properly on the tester.

Sounds like the trailer load doesn’t agree with the truck control module.

[Aussieguy]

Originally Posted by aircommuter

Sounds like the trailer load doesn’t agree with the truck control module.

multi meter will tell you if each pin is working and how much voltage it has


5 minute job ... you just need someone to operate brakes turn signals etc while you test

[Comanchecreek]

I had the same issue with my Chevy. Turned out to be the turn signal module. Trucks of that vintage use a multi pronged module that separates the truck lights from the trailer lights. They are also fused separately. YouTube would be a great place to start to find the location and procedure on how to replace it. The turn signal switches are not like the old days. Mine was 60 bucks, and was a ten prong connector. My guess is your Ford is similar.

[aircommuter]

Originally Posted by Aussieguy

multi meter will tell you if each pin is working and how much voltage it has


5 minute job ... you just need someone to operate brakes turn signals etc while you test

While the meter will give information it is still controlled by the module which will shut off the feed for the load being too low or high. The module could also be defective.

[MR.M]

Originally Posted by aircommuter

While the meter will give information it is still controlled by the module which will shut off the feed for the load being too low or high. The module could also be defective.

I would think if you tested the lights at the trucks 7 way with no load and got good readings then it would work hooked up with some load even leds

[aircommuter]

Originally Posted by MR.M

I would think if you tested the lights at the trucks 7 way with no load and got good readings then it would work hooked up with some load even leds

Those modules have a mind of their own sometimes.
Lots of large wires going to the turn signal switch are a thing of the past and have been for a while. Three or 4 small wires send codes to the module and they do the work, sometimes the module will be controlling relays for the trailer circuits.

[EVOlutionary]

Well finally got it fixed. Took the truck to a specialty 12V Auto electronics shop. They found the problem was a bad connection in a wiring harness plug somewhere up under the back end of the truck. I think it’s where the trailer tow plug sub harness plugs into the main harness. They ordered replacement plugs/harness section, Re pinned the wires, and everything works good as new.

[Reverse_snowbird]

Originally Posted by EVOlutionary

Well finally got it fixed. Took the truck to a specialty 12V Auto electronics shop. They found the problem was a bad connection in a wiring harness plug somewhere up under the back end of the truck. I think it’s where the trailer tow plug sub harness plugs into the main harness. They ordered replacement plugs/harness section, Re pinned the wires, and everything works good as new.

Fantastic news! Glad you got it fixed.

[cmulvey]

Originally Posted by EVOlutionary

Well finally got it fixed. Took the truck to a specialty 12V Auto electronics shop. They found the problem was a bad connection in a wiring harness plug somewhere up under the back end of the truck. I think it’s where the trailer tow plug sub harness plugs into the main harness. They ordered replacement plugs/harness section, Re pinned the wires, and everything works good as new.

Thank you for follow up with solution.