Tail lights intermittently not working

Hi friends, I have a 2017 Tab 320 S. I noticed while doing a pre-trip walkaround this past weekend that the right tail light wasn't working. I got my screwdriver and voltmeter out, unscrewed the right tail light out to see what was behind it and before I did anything the left tail light stopped working too.

I took a closer look and the left tail light was actually still turning on, but quite dim. This made me suspect an issue with the connection to the TV so I unplugged the pigtail and checked all 7 pins on TV side with the voltmeter and they all seem to be working fine.

I plugged the pigtail back in and measured the voltage at the trailer battery with the TV turned on and only measured 12.9V. The pins on the TV were putting out something like 13.6.

A short while later, both taillights magically started working perfectly again. I checked the voltage at the battery and now it was 13.6 as expected.

So my theory is that the pigtail is bad and I should throw it out and get a new one. I'm not able to reproduce the issue anymore though so I can't be sure that's actually the problem :(

Has this happened to anyone else? Am I on the right track? Is it easy to replace the pigtail?



  • SLJSLJ Member Posts: 407
    edited October 24
    Since it's more than one light I'd start by checking ground. Ground is used by all of them. Check all the connections where the pigtail connects first. Sometimes it's as simple as a nut loose on a post or dirty/loose contacts in the seven pin plug.
    2021 T@B 320 S Boondock
    The Finger Lakes of New York
  • MuttonChopsMuttonChops Member Posts: 1,554
    PeterTAB said:
    . . . my theory is that the pigtail is bad and I should throw it out and get a new one.

    Has this happened to anyone else?  [Muttonchops:} Not myself, most likely others have you used the Forum Search Feature.

    Am I on the right track?  [Muttonchops:} My guess is No, pig-tail itself not the issue useless you can re-create the issue by flexing the cable near the connection point.

    Is it easy to replace the pigtail? [Muttonchops:} Yes.
    If my rig would start by searching for loose wire terminal connections.
    First location being the pig-tail to trailer Junction Box.
    Next location(s); inspection wiring and connections of wire runs in Alde compartment and up behind that compartment.

    Focus on damaged wires or loose connections before replacing pig-tail.

    '18 320 Spitched axle, 3020HE; PNW based
    TV: '17 Colorado V6 Z71 4x4, Tow Package, GM Brake Controller
    Adventures:  50   Nights:  287 
  • Sharon_is_SAMSharon_is_SAM Administrator Posts: 9,398
    Any chance the 7 pin was wet?
    Sharon / 2017 T@B CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
  • HomebodyatheartHomebodyatheart Member Posts: 2,469
    I was having similar issues and finally figured out that the 7 pin connector at the TV is actually plug and play on the backside. Now when I plug in my trailer I use both hands and push the connectors in from both sides. Problem solved! Now to remember this winter to not back into a snow bank that was frozen hard, bending the connection bracket!  
    2017 T@B 320 Max S silver and cherry red, L@dybug ("Bug" aka my esc@pe pod), TV 2015 Toyota Highlander aka Big Red
  • PeterTABPeterTAB Member Posts: 6
    edited November 16
    Fixed! The problem was corroded contacts in the seven pin plug (trailer side).

    I found this video that was quite helpful: https://www.youtube.com/watch?v=H6occ6I_6HU&t=134s

    I didn't have a brass pipe cleaner so I just wrapped a piece of sandpaper around a screw and brushed both sides of the plug contacts. To my amazement the pins turned some kind of yellow color as I cleaned them (copper? brass?) and they're actually not supposed to be gray!

    I then picked up some WD-40 contact cleaner for $8 and blasted the guts of the plug to wash out all the gunk (sandpaper sand, oxide powder, dirt). And it's as good as new so far. Fingers crossed, hope the lights stay on all next week (going to Joshua Tree and Sequoia & Kings Canyon NPs for 5 days).

    I also spent a bunch of time cleaning out the ground wire connectors in the junction box under the trailer but I don't think that was really necessary. They were only a little oxidized, virtually pristine compared to the seven pin plug.
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