Wire Gauge Needed for Brake Circuit on 28-Foot Enclosed Trailer

Question:

I have replaced the brakes 12 in. with all new parts and have changed controllers and still my brakes do not work very good. I started checking my voltage and with the brakes hooked up I only have about 10 volts at the brakes. If I unhook the wire just in front of the brakes my voltage is 13.6 but as soon as I hook the brakes back up the voltage s. What should the voltage be at the brakes. I thought they should still be close to 13 volts. The wires that run from the main primary wire to the brakes is pretty small probably 18 ga. Could this small of a wire not be heavy enough to carry the load for the brakes to function properly. I have good grounds and the brakes are all adjusted properly. Maybe when the trailer was built they are using smaller wire to cut there costs. The trailer is a 28 foot enclosed car hauler and the brakes never has been very good even when it was new. I have thought about rewiring the whole brake system with heavier wire. Do you think this would help? Thanks

asked by: Robert J

Expert Reply:

I am not sure what wire it would be that you are disconnecting but with a trailer brake controller set for maximum output/boost you should definitely read more than 10-volts at the brake assemblies.

18-gauge wire is too light for a trailer brake circuit. At minimum you should use 12-gauge wire # 12-1-1 on a short trailer, but on a 28-foot trailer you need nothing less than 10-gauge wire # 10-1-1.

With 18-gauge wire if the trailer is a tandem axle with 4 brakes then the problem will be even worse than if it were a single axle trailer with only two brake assemblies.

expert reply by: Adam R