Trailer light grounding issue?

[Luc Lafreniere]

Hi,

So I had a damaged marker (yellow) clearance light on my wheel fender. I proceeded to replace it but in the process discovered that ALL my trailer lights weren't working.

To make a long story short, I discovered that when the trailer is NOT hitched to my SUV, the lights don't work. But when it is, the lights work. I also could replicate the same thing when not hitched by attaching the safety chains/cables. Essentially, the trailer seems to need to be grounded to the hitch of the car for the lights to work.

Now, this seems really odd to me. Essentially the lights seem to rely on a good contact between the trailer and the hitch which seems like a potential issue. If contact isn't good for some reason, lights are going to go out.

My wiring harness on the car was installed by the dealer a few months ago but of course, maybe they screwed up the install?

Any ideas would be appreciated or if it's just confirmation that this is normal.

Merci!

 

[Chad]

The white wire on your vehicle harness should be grounded to the car chassis. It may not be grounded properly. You should be able to check it if you have a multimeter with continuity or resitance options. Just put a probe to the exposed post on your vehicle harness(white wire) and the other probe to a good (non-painted)metal surface on your car. For continuity it should beep, if you choose the resistance option it should read very close to zero.

The other scenario would be reverse, the white wire on the trailer harness may not be grounded properly, that should be easy to check as you can most likely follow that wire on the trailer to make sure it's still secure.

 

[Luc Lafreniere]

Excellent info. Thanks. I'll have a look later tonight. I do have a multimeter, I'll report back with what I've found.

 

[Luc Lafreniere]

I couldn't verify numerically the issue, but I found the white wire on the trailer hanging slightly out of the plastic protective wrap. It seems it was on the tight side and was ripped from the ground point/screw underneath the tongue (small and VERY rusted screw). I'll need to remove that with some vice grips and replace it along with extending the wire a bit so that this doesn't happen again.

Thanks for the help. I'm confident this is the issue.