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How to Test for Bad Trailer Brake Wiring on 18' Flatbed Trailer  


I have a 18 foot flatbed trailer that when hooked up to my 2022 Ram 2500 it shows an error on the dash that says Check trailer brake wiring Trailer brakes disconnected. The trailer lights always work and never go out its just the brakes. The brakes will not work when the error is on the dash and the error isnt constant. It seems like a loose wire or connection but I can not find one. I tow other trailers with my truck and I do not get an error on those trailers with brakes. When checking the wiring inside the drums, I found one seal that was bad. The drum was covered in axle grease as well as the brake magnet. I think thats what its called. I figured since it had grease on it it wasnt allowing it to connect to the metal drum. After replacing the seal and cleaning everything it still gives me an error. My next step I guess would be replace the wiring from where it comes off the frame to the brakes. Hoping the problem is the wire inside the axle. Looking for advice on potential fixes that I am missing.


Helpful Expert Reply:

You are definitely heading in the right direction to get the brakes on your trailer working properly. Since the problem is intermittent and not constant that means you have damaged wiring and/or a bad ground somewhere so you need to check the wiring (like you're done) for and damage, cuts, or bends, as well as any connection points like butt connectors or ground locations. If your trailer has standard butt connectors I recommend replacing those with heat shrink connectors like # DW05745-5 which do a better job at protecting the connections against the elements.

Also be sure to check the 7-Way connector on your trailer. It will help to open that up and look at the connections from your wiring to the pins as these can get loose over time as well.

Attached is a helpful article for you to check out. If you still aren't able to get it figured out please let me know what else you've done and I can offer some more assistance.

expert reply by:
Jon G

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