Troubleshooting Trailer Brakes Getting Only 8 Volts Of Power

Updated 07/27/2025 | Published 05/01/2017

Question:

I put new shoes on the travel trailer on all 4 wheels the drum, back plate and magnet were in good shape The brakes are working but not stoping like it did before I turn the brake controller all the way up and Im only getting 8 volts to the brakes and 8 volts to the plug on the back of my truck 2008 Dodge Ram hemi also pulled the emergency pin Plug on the travel trailer and still it was 8 volts to the brakes Im wondering if my brake controller is bad

asked by: Randy

Expert Reply:

If you are only getting the 8 volts when you pull the pin using a meter like # PT89ZR, that has nothing to do with your brake controller as the breakaway battery is powering that from the trailer itself. You can confirm your brake controller is working properly by checking the 5 o'clock pin on your 7 way with your meter when the trailer is disconnected while having someone hit the manual override on your brake controller.

You most likely have a bad ground in your wiring on your trailer. Check the grounds near your brake assemblies for corrosion or rust and make sure there is a clean metal to metal connection. Check your voltage again, and if that didn't solve it, check all other trailer grounds. If that doesn't solve it, you will need to trace your brake wires to locate a short. Check visually first and then with a tester. Replace wire as needed.

Your brake magnets could also be an issue, so I recommend testing them with a battery and your voltage meter. I've attached an article to help. While you are in there testing magnets, you will want to make sure you have adjusted your brakes shoes properly. There should be a slight drag on a spinning wheel when adjusted properly.

expert reply by: Jason S

Paul

7/27/2025

I connected my battery charger to my trailer brakes through my junction box and then checked my voltage with meter at several spots in my wiring going to my brake and only have 8 volts.