Why Would Trailer Brakes Lock Up with One Tow Vehicle But Not Other

Question:

Why would my trailer brakes be locked when hooked to one truck and not the other?

asked by: Jack

Expert Reply:

Normally when we see this problem it's on setups that use 6-way trailer wiring. The reason is there are two generally accepted ways to wire up 6-ways and the only difference is the 12 volt accessory circuit and the brake output circuit are swapped which means that if you go to connect a trailer and tow vehicle that are using the opposite setup the brakes are locked up. So the simplest solution is to flip these two circuits on either the tow vehicle or the trailer. Check out the attached wiring diagram.

expert reply by: Jameson C