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GMC Forum: Trailer Brake Problems
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  #1  
Old 05-15-2020, 07:03 AM
asylum asylum is offline
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Default Trailer Brake Problems

I've searched quite a bit and I've also done a heck of a lot of testing trying to figure out why my integrated brake controller box is not recognizing my trailer. Here is what I've done over the past couple months:

1. Replaced relay on top of spare. Worked for about 3 miles then brake messages started up again and then no brakes recognized.

2. Found one grounding problem on trailer wiring. Fixed that. Again, brakes worked fine for about a mile then messages started up again and then no brakes recognized.

3. Used test light. connected to ground pin and then touched trailer brake pin. I initially get one bright blink of the light, and then continual weaker blink. If I engage the trailer brake lever, nothing changes on the test light. I also tested all wiring into the wheel magnets and I get the same blinking light.

4. I pulled the pin on the emergency box and wheels lock up.

5. I connected my trailer to a friend's truck who uses and aftermarket brake controller, brakes locked up on trailer.

When the controller does work, when activated I can hear a clicking in the fuse box under the hood. The fuse to the controller is good.


So with all that said, I think I can rule out the trailer wiring.

I did take the dash panel off to get to the back of the switch. There are like 5 or 6 wires going into that switch. I can't find anything on how to test or what wires to test. I don't know if the problem is with the controller or maybe the relay (even though it is only three months old).

Any help and suggestions greatly appreciated.

Bob
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  #2  
Old 05-16-2020, 01:19 PM
98trck 98trck is offline
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Drives a '11 sierra 1500
 
Join Date: Feb 2011
Location: Chandler Az
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there are different relays that have different internal wiring schematics
I have purchased new relays and the wrong one is in the box
look at the side of the relay itself it has the wiring schematics on it
compare it to the original
PETE
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  #3  
Old 05-16-2020, 02:18 PM
asylum asylum is offline
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Thanks Pete,
After months of chasing this gremlin, I finally found the problem. It wasn't in the truck at all. Pesky wiring on the trailer was the problem, even though I got mixed messages when a friend hooked up and all was good. Wire was intermittently making connection.
Phew, glad it wasn't a problem in the truck that needed traced out.

Bob
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  #4  
Old 05-21-2020, 10:13 PM
98trck 98trck is offline
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Location: Chandler Az
Posts: 276
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Yay
intermittent electrical are the worst
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