Forum Discussion

snebor's avatar
snebor
Explorer
Jul 28, 2015

Intermittent Brake Light Issues

Hello - I'm having some intermittent trailer brake light issues and I'm hoping someone can steer me in the right direction

- we just bought a 2008 pop up trailer. The seller dropped it off and all lights were working. It has a 7 way plug
- a new wiring kit (with electric brake wiring) was installed on my 2009 santa fe by a hitch shop
- at the hitch shop, the mechanic has an apparatus to test all lights. Everything works (I've been back a couple times to re-check)
- at home, the brake lights on the trailer intermittently don't work. Everything else works fine
- sometimes neither brake light works. Sometimes just the driver side light works. Sometimes both work. Wiggling the 7 way cable doesn't seem to help. Pulling it out and plugging it back in sometimes fixes the issue
- the brake bulbs lights are three way lights. The running light portion always works. Based on my understanding, I think this rules out grounding issues
- I hooked up my car on a different trailer. I saw the same issues (although it seemed less common). However, the mechanics apparatus at the hitch shop always works
- I also hooked up a multimeter to the vehicle 7 way plug. The brake lights always show correct voltage on the multimeter
- I also hooked up a 9v battery to the brake lights on the trailer. This always works perfectly. The lights always turn on

To me, it seems like a car problem, but I don't know what the problem could be. It's weird that the mechanics test apparatus works and it's hard to convince the mechanic of an issue given that it works at his shop

I'm wondering if the issue could be on the brake relay or wiring harness. Perhaps it's the kind of issue where only real world voltage/current draw will present the problem. A simple 7 way test harness isn't quite the same as an actual trailer where the bulbs and brakes draw more current than a test harness


Does anyone have any suggestions/hints/ideas?


Thanks a bunch



PS - I've got someone coming over with a different vehicle and I'll try hooking it up to the trailer. I've also purchased a simple 7 way tester from amazon. I'll post my findings once I try these

10 Replies

  • Gene_Ginny's avatar
    Gene_Ginny
    Explorer
    Jul 29, 2015
    Spray the 7 pin connectors with a liberal dose of WD40. I have "fixed" a lot of electrical issues with that stuff and it is a cheap and easy test to do.
  • snebor's avatar
    snebor
    Explorer
    Jul 29, 2015
    Hmm - I found a couple posts where people had problems with this part (56078)with a 2009 santa fe. This has got to be my problem

    http://www.etrailer.com/question-41610.html
  • snebor's avatar
    snebor
    Explorer
    Jul 29, 2015
    ChooChooMan74 wrote:
    Brake lights, turn signals, and 4 ways use the same wire and filament on the trailer. If the turn signals and 4 ways are working properly, and just the brake lights not working, I suspect that the issue may be your 3 to 2 converter.



    I opened up the work that the mechanic did. everything looks good. The car ground ties into the 7 way plug. All plugs are tight. I see no issues here.

    Note that turn signals do not work. i.e
    - running lights work. This includes dimming the 3 way brake/running light bulbs
    - electric brakes work
    - left and right brake light/turn signal are intermittent

    I have to think it's the 3 to 2 converter
  • ChooChooMan74's avatar
    ChooChooMan74
    Explorer
    Jul 28, 2015
    Brake lights, turn signals, and 4 ways use the same wire and filament on the trailer. If the turn signals and 4 ways are working properly, and just the brake lights not working, I suspect that the issue may be your 3 to 2 converter.
  • enblethen's avatar
    enblethen
    Nomad
    Jul 28, 2015
    This harness taps into system with no trailer package.
    Check to make sure each of the connectors are plugged into the rig firmly.
    The ground connection is very important. Make sure the installer cleaned the paint off the rig or used a factory ground point in the taillight.
    Curt installation sheet.
  • snebor's avatar
    snebor
    Explorer
    Jul 28, 2015
    GMandJM wrote:
    Get a 7-pin (pole) plug tester. It will tell you what's not working (if anything).

    Usually it's just a pin not making proper connection because of dirt or corrosion.



    Yeah - I was thinking along that line as well. However, I fiddled with the trailer plug contacts quite a bit. I cleaned them out, sanded the contacts and adjusted their position. None of this seemed to make it better or worse. Furthermore, if it was a contact issue, I would think that wiggling it would change the behavior (ie. make the lights work or not work). This doesn't seem to be the case. I only see different results when I fully unplug and re-plug in the 7 way plug
  • snebor's avatar
    snebor
    Explorer
    Jul 28, 2015
    enblethen wrote:
    Did the shop install a connector into the TV wiring harness or tap into the Sante Fe's lighting harness?
    Does it have factory towing package?
    The converter three to two modules can create strange results.
    ***Link Removed***


    Good question. I'm not quite sure. The vehicle does not have the factory towing package. I would have to think it's a wiring harness similar to the one you posted

    Based on the invoice, I think this is the one that was used: http://www.curtmfg.com/part/56078
  • GMandJM's avatar
    GMandJM
    Explorer
    Jul 28, 2015
    Get a 7-pin (pole) plug tester. It will tell you what's not working (if anything).

    Usually it's just a pin not making proper connection because of dirt or corrosion.
  • enblethen's avatar
    enblethen
    Nomad
    Jul 28, 2015
    Did the shop install a connector into the TV wiring harness or tap into the Sante Fe's lighting harness?
    Does it have factory towing package?
    The converter three to two modules can create strange results.
    Harness

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,256 PostsLatest Activity: May 21, 2025