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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), GMC Mechanic
Category: GM
Satisfied Customers: 29428
Experience:  GM Grand Master Technician 2007. 14 years experience.
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my trailer brake lights work on the right side only, my left

Resolved Question:

my trailer brake lights work on the right side only, my left side turn signal works,but my right side lights up both, i get the signal from the trailers plug also. all the truck taillights work properly, where should i look next.
Submitted: 5 years ago.
Category: GM
Expert:  GM Tech (Cam) replied 5 years ago.

GM Tech (Cam) :

Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

GM Tech (Cam) :

Confirm this is only on the trailer, correct?

GM Tech (Cam) :

meaning the truck signal lights and brake lights are good?

Customer:

yes they are working properly on the truck with the trailer connected and unconnected.

GM Tech (Cam) :

OK they are seperate. So, on the plug, is there a proper left and right signal with the signals on?

GM Tech (Cam) :

the truck signals and brakes are independant of the trailer and the brake/signal is a single wire for each side on the trailer.

Customer:

when checking on the truck side of the connection, the left side terminal has no power when the brakes are applied, when the turn signal for the left side is on, there is only power on the left side, when you turn on the right side turn signal, you get power on both the left tern\minal and right terminal.

GM Tech (Cam) :

Now the signal flasher which also controls/splits the brake and turns for the trailer is notorious for failing, but we need to make sure it is not wiring.

GM Tech (Cam) :

same for brakes then?

GM Tech (Cam) :

And right signal only does right side on the trailer not both?

Customer:

the right turn signal also does both on the trailer. what it does at the truck connection also does on the trailer

GM Tech (Cam) :

Ok so try this, remove the TRLR RT fuse in the left dash fuse block, what happens?

Customer:

ok will go out and do

GM Tech (Cam) :

sure thing.

Customer:

when i pulled the trailer dash fuse, the right trailer light quit, but the left trailer light is still flashing.

GM Tech (Cam) :

ok, so that means the wires are not crossed and means it is the flasher on the back side of that fuse block

Customer:

okay so i will need to replace that flasher control

Customer:

i am not use to this type of flasher.

GM Tech (Cam) :

yes, replace it.

Customer:

thanks for your help.

GM Tech (Cam) :

This is a long black big relay and you need to remove the dash trim under the column to get at it

Customer:

okay. anything else i will need to know to replace it

GM Tech (Cam) :

Nope, plug and play unit.

Customer:

thank you.

GM Tech (Cam) :

Please reply back if you need additional help or press ACCEPT If my answer was helpful. You can reopen it at any time by replying to it and I will answer ASAP. PLease keep in mind that as experts on this site, we are only compensated for our time spent helping customers once ACCEPT is selected. Be sure to bookmark this page (CTRL D) to reply with results or ask more if you need. Thanks again for using Just Answer. Cam.

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