Left Trailer Stop/Turn Signal Issues

[mrbrett]

I have hooked up a flat 4 pin trailer to my 2003 Sport Trac and all the lights work except for the left stop-turn.

To troubleshoot:

I checked the fuse in the dash board (OK) and under the hood (also OK) for the various trailer-related circuits.

There is no power at the connector under the bumper for the middle (yellow) pin. This has been confirmed with a test light. Right turns work OK in all regards.

I replaced the flat 4 pin connector, no improvement.

While replacing the connector, I noticed the wire in the yellow insulation was blackish (rather than copper) so as a next step I followed it back through the harness further, to roughly beside the spare. I then tried splicing in a section of wire from there to the bumper connector. Still no improvement.

What's the next step? Continue following that yellow wire back to wherever it starts? I'd rather not disturb more OEM harness than I have to.

Plan B - Just get a powered universal kit and call it a day?

I am open to suggestions.

 

[ncranchero]

Did the vehicle left stop/turn work on the vehicle, before adding the trailer adapter?after?

 

[mrbrett]

Everything works on the vehicle - it's the factory trailer wiring on the vehicle that seems suspect.

 

[wifes2011xlt]

Here is a handy wiring guide, just as an FYI...http://www.hopkinstowingsolutions.com/support/wiring-guides.html

Dumb question, but did you try replacing the bulb?

When you spliced into the wiring, did you do it at the harness or at the wiring that connects to the harness?

Sounds to me like a faulty harness, in which case just pick another one up for ~15-20 bucks. If it's the vehicle wiring itself, then you'll have to do it the old fashioned way and splice directly into the left turn signal leads. I'm thinking harness at this point though.

 

[mrbrett]

Thanks for the guide! That confirms what I found and tells me what color wire to look for in the taillight.

I swapped bulbs left to right and cleaned the contacts, and ultimately used a test light at the connector to verify the issue is upstream of the plug at the bumper.

It's definitely the vehicle harness, I think from here my best option is to tap into the left taillight wiring for the trailer left stop/turn. At least that's easy to get to.

 

[mrbrett]

Update: I ended up patching into the turn/stop signal right at the tail light and it works great with the trailer. Seemed to be the lesser of two evils compared to digging through a long piece of harness looking for a fault in the OE trailer wires.

Thanks for the help.

 

[wifes2011xlt]

Good deal.

Just pulled my utility trailer out to start moving things into storage this winter. Wouldn't you know it, my trailer lights didn't work. My ground got corroded. Used a brush attachment on my dremel to clean up and good as new. Happy towing.

 

[429CJ-3X2]

Update: I ended up patching into the turn/stop signal right at the tail light and it works great with the trailer. Seemed to be the lesser of two evils compared to digging through a long piece of harness looking for a fault in the OE trailer wires.

Thanks for the help.

I had the same problem, and fixed it the same way.