Installed New Brakes, Hubs, and Brake Controller and Brakes will Only Lock Up when Trailer is Lifted
Updated 08/15/2025 | Published 07/18/2025
Question:
I have a trailer with 2 ,8000s lb axel just put all new brakes , magnets,hubs brake controler and brake come on but not enough to stop the vehicle It shows 4.5 volts out of the controler at the 7 pin on the truck If I jack the trailer up all 4 wheels lock up But don’t lock up on the ground How much voltage should go to each wheel?
asked by: Brent
Expert Reply:
Hello Brent,
Did you check the voltage while pressing down the brake in your truck, or while doing the manual override on the controller?
When you do the manual override you should be getting close to 12 volts, if you aren't then that is going to be the issue. Or a bad ground on either side can cause all kinds of issues, make sure they are on a good clean metal surface.
Did you break-in the new brakes? I attached a help article where you will want to follow step 4 on breaking in your new brakes.
I would start with those 3 things, if it doesn't fix the issue let me know the voltage you are getting from the 7 way with the manual override, the voltage at your brakes, what kind of brake controller you are using.
Or if you already fixed the issue, please let me know what it was.
Kate F.
8/15/2025
Hey Brent, Did you have a chance to check the voltage with the manual override on your brake controller? I'm really curious to know if that helped solve the issue with your trailer brakes not locking up on the ground. Let me know how it went, as it could really help others facing similar problems!