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Very Odd Problem- Right Taillight

HomebodyatheartHomebodyatheart Member Posts: 2,497
in Battery/Electrical & Solar
I have a 2017 320S. When testing my signals yesterday before towing my right tail light didn’t light up with the brakes on. However it does light up for the R turn signal and again for the emergency flashers. I removed the light and the three wires look to be in perfect condition, the storage cavity is spotless. We wiggled the connection at the TV, removed and reinserted it multiple times, it is properly lubed with dielectric grease, looks clean. No problems with any other tail lights/signals. Any other ideas and fixes? Thanks!
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
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    HoriganHorigan Member Posts: 617
    Have you confirmed you're getting the correct signals from the TV receptacle?

    On the front frame rail under the tub there is a junction box for the 7 pin connector.  You can confirm proper signals there to isolate whether the issue is in the 7 pin cable or the 320S wiring.
    Rich
    2019 T@b 400
    2013 Toyota Highlander 3.5L V6
    Bellingham WA
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    BaylissBayliss Member Posts: 1,299
    @Homebodyatheart, if I am reading your question correctly, the right brake light is the only light that is not illuminating.  In other words, the taillight, turn signal and emergency flashers are working.  Am I correct?

    If so, I would check the 7-pin connections (tow vehicle receptacle and trailer 7-pin plug) to be sure both are clean and dry.  You will also want to look specifically at the pin connection for the electric brakes.  It's possible that there is some slight corrosion there.  Spray some electric connector cleaner on those connection and then follow it up by adding some dielectric grease.

    Also, I agree with @Horigan's suggestion to check the wire connections in the wiring junction box on the front frame of the trailer.  Yours should be wired similar to my 2019 320 S, so check the #1 (far left) pin for the brake wire connections and the #7 (far right) for the ground wire connections.  Either may be loose.  You can see my wiring diagram for the junction box in this discussion thread:

    https://tab-rv.vanillacommunity.com/discussion/10884/exterior-light-question
    2019 T@B 320 S Boondock Lite; 2007 Toyota Tundra 4x4
    (Alde: 3020; Refrig: Isotherm Cruise 65 Eleg; Battery: BB 100Ah LiFePo4; Solar: Renogy 100Ah Suitcase; Victron BMV-712; Pwr Cntr: PD-4135KW2B; EMS: PI-HW30C)
    Greg & Marlene (Tucson, AZ)


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    MuttonChopsMuttonChops Member Posts: 1,596
    Homebodyatheart said:
    . . . right tail [brake] light didn’t light up with the brakes on.
    . . . it does light up for the R turn signal and again for the emergency flashers.
    . . . No problems with any other tail lights/signals.
    I agree with @Horigan that you should check for the correct voltages at the TV 7-Pin.

    It is difficult to think of any trailer reason for the Turn Signal & Flasher to function but not the Stop light.
    For reference:

    '18 320 S,  pitched axle, 3020HE; PNW based
    TV: '17 Colorado V6 Z71 4x4, Tow Package, GM Brake Controller
    Adventures:  51   Nights:  322  Towing Miles 41,200+
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    HomebodyatheartHomebodyatheart Member Posts: 2,497
    Thanks for your quick responses and links. I’ve got some investigating to do… fingers crossed! I won’t be towing again until Monday, but I can play with it sooner. 
    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
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    DalehelmanDalehelman Member Posts: 2,410
    edited July 2021
    Some vehicle tow packages include a separate fused area specifically dedicated to the trailer. So that if the trailer wiring malfunctions it will not effect the tow vehicle. It seems I remember seeing separate fuses for each Circuit. Including one for the left and right brake lights. Generally they are on the same circuit as the turn signal since they share the same bulb or LED. These fuses would be under the hood, probably on driver side. Or in the driver foot well area. Probably well out of sight. Check vehicle owners manual. For trailer towing and fuses. Maybe someone else has better Recollection.
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    DalehelmanDalehelman Member Posts: 2,410
     If your wiring was done after market. The installer may have installed some sort of sub panel to prevent the chance damage to any of the electronics in the tow vehicle. If something go wrong with the trailer. Sounds like a good idea to me. Just brainstorming. If it were after market installed I would go back to them. This is a very strange problem.
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    HomebodyatheartHomebodyatheart Member Posts: 2,497
    @Dalehelman it was after market, installed by the Toyota Dealer. I’ll check with them next week, and probably also call my usual car fixit guys at Tire’Rama. They are reasonable and usually can fix whatever I bring in. Thanks Dale!
    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
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    Grumpy_GGrumpy_G Member Posts: 453
    On the trailer side there is only one connection running from the plug to the tail light, and there is only one "bulb" (set of LEDs) for both brake light and turn signal. If the turn signal works I can't come up with a scenario where the brake light doesn't. 
    Does the Highlander have separate turn signals and brake lights ? IIRC the vehicle requires some sort of module to properly drive trailer lights. As already suggested make sure the tow vehicle puts out voltage on both the left and right turn/brake pins (3 and 9 o'clock position from the notch). 
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    DalehelmanDalehelman Member Posts: 2,410
    We already know the light is getting power. Because the turn signal and the emergency flashers work. There must be something in the TV that is separating the brake light circuit. Generally when trailer lights do strange things it can be traced back to a bad ground. But I don’t think so in this case.
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    DalehelmanDalehelman Member Posts: 2,410
    Put a test light on the 3 o’clock and 9 o’clock from notch of the seven pin of the tow vehicle. If they both light then it must be in the trailer. If one doesn’t light then the problem is in the TV. Ground the test light to the vehicle frame then use the probe on each of the  fore mentioned terminals. 
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    jtalarekjtalarek Member Posts: 19
    I had a similar problem with the right tail light; the turn signal and brake light did not work but running light did work.  It was a bad light, installation of new bulb did the trick.
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    DalehelmanDalehelman Member Posts: 2,410
    Most foreign cars have separate brake and turn signal lights. American trailers don’t. There is a module generally near the 7 pin that adapted the foreign wiring to the American. That could likely be the problem. It is fairly cheap and easy to replace 
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    DalehelmanDalehelman Member Posts: 2,410
    edited July 2021
    This is my guess as to what is malfunctioning.
    You just cut off the flat four plug and reattach the wires to the 7 way.
    I want to recommend this product at Amazon<BR><BR>CURT 56130 Non-Powered 3-to-2-Wire Splice-in Trailer Tail Light Converter, 4-Pin Wiring Harness<BR>by Amazon.com<BR>Learn more: https://smile.amazon.com/dp/B0049CI05W/ref=cm_sw_em_r_mt_imm_awdb_8RCS3NV9G1VGYDMJH6CV
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    MuttonChopsMuttonChops Member Posts: 1,596
    Has this been resolved - - repair delayed - - working on it's own now ? ? ?
    '18 320 S,  pitched axle, 3020HE; PNW based
    TV: '17 Colorado V6 Z71 4x4, Tow Package, GM Brake Controller
    Adventures:  51   Nights:  322  Towing Miles 41,200+
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    DalehelmanDalehelman Member Posts: 2,410
    I talked to homebody a couple of days ago. It is apparently working fine now.
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    DudleeDudlee Member Posts: 24
       Intermittent electrical problems are a real drag unless you own an old Triumph, MG , or Jaguar. You learn to love them then. :}
    —  2019 320 S Boondock, 2016 Nissan Frontier, Sonoma County
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    HomebodyatheartHomebodyatheart Member Posts: 2,497
    Thanks Captain @Dalehelman for the update! @MuttonChops sorry for the radio silence… I had an odd light when I plugged it in to head home, so I unplugged it and made sure that this time I inserted the plug in straight and all the way. Voila! It worked like a charm! I think the original problem may well have included “operator error” from my crew person before I left home. It looks pretty clean and still has a fair amount of dialectic grease in it. I suspect investing in a cover cap might be a good idea! Thanks again to everyone for your help! I learned some new things in all this( and will probably plug it in myself next time…)

    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
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