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Trailer Wiring Help

5K views 30 replies 10 participants last post by  Redcrew 
#1 ·
OK my right turn signal and brake light stopped working. running light works. I'm getting nothing at the connector for the RH stop and turn all other pins read good. Took the plug apart and read the wires same result. Swapped the two relays up front, swapped the relays in the kick panel. I'm out of ideas. Any help would be great.
 
#2 ·
Something to check is the relay installation is different between the auto and manuals. I think it was the autos where you only use 2 relays in the kick panel harness and the manuals use all 3. Worth a double check anyways.
 
#20 ·
Sorry guys just got back from a camping trip(yes in a tent). Been gone all week.
Zero six I swapped the relays. The two in the eng compartment I just swapped the RH for the LH nothing changed. The ones in the kick panel I swapped the whole harness from my sons truck. Still the same, I'm stumped. Ill try to take another look at this this week.
 
#22 ·
Thanks everyone for the help. At this point it may be the BCM. I have no way to check that and I don't want to take it to the dealer to troubleshoot as that would be expensive so I'll see if I can find a workaround for now. I dont use my trailer that often so I have time. Just hate something not working (OCD).
 
#23 ·
Did you try to unplug beside left frame rail and test there for RH turn and brake? On a trailer, turn and stop is the same wide with alternate or continuous power in it. By my side before doing any fusebox/relay search, i would unplug there because i already had trouble with rear plug kit (from frame rail to rear connecter).

Before pay alot for troubleshooting! I also replaced my oem.connecter by a new aftermarket one right into bumper, with downside angle so water and salt does not stay in it. Better look and use. And protected from road hazar.
 
#24 · (Edited)
I presume your receptacle is the 7 way blade style? Also, the trailer lights do work on possibly another truck (friend, relative)?
If it's dead at the receptacle on your truck, I'd check the blade connector on both the truck and trailer. I've had connection issues in the past - usually due to grounding, wire connections incorrect, or broken pins.

Agree with chijusa comments - If you are around salt or water often, the corrosion can prevent the connection. I may eventually integrate mine to the bumper too.

I can relate to the OCD - wanting it fixed now, it being bothersome, and it's always on your mind. Hope it gets remedied soon.
 

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#26 ·
I haven't figured anything out yet. I've read all my wires front to back and haven't figured it out. All I can say is look at all the suggestions on here Maybe you'll have better luck. Also i have a light tester so I dont have to use the actual trailer. It will also make sure its the truck and not the trailer. Good luck.
 
#27 ·
By my side I confirm truck side. Tested output on truck plug and nothing right hand. And tested trailer with battery and all is OK.

Aparently, flasher relay work, but No power. I'll check electrical schema to see what are the option, knowing that trailer flasher circuit is pretty simple, but power on the line come from somewhere...
 
#28 ·
Not sure if this helps from a similar posted question on e-trailer. I recently installed some slim led's to my hitch mounted 2 bike carrier for added safety on a recent trip. I probably should have taken my time as I was in a hurry to get it done........on my 1st attempt I followed the trailer wiring instructions vs. reviewing the wiring schematics found on the truck plug lid(7 way). Of course it worked once I realized what I had done.
Sounds like a broken connection/ground issue if the right side is not working correctly.
 
#29 ·
What i'm about is a unmodified oem trailer harness that was working before i follower a trailer plug wiring diagram... That was wrong.

After that, i checked all fuses, changed a bad one, rechecked all, and No power on right side brake/flasher. Then I changed relay from left to right, and still nothing. So anything refering to an "after oem harness" does not intetest me. It's the OEM electrical system, body electrical and trailer circuit that i've to scan for trouble.

But thanks for trying to help US. :)
 
#30 ·
Looking at FSM, i have courant to my right turn signal relay. And out of it. So trouble is into harness between relay and rear plus. More tests soon.
 
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