What is the Proper Gauge Wire for Installation of a Brake Controller and Trailer Brakes

Updated 12/30/2009 | Published 12/29/2009

Products Featured in This Question

10 Gauge Wire - Blue Primary - Per Foot

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Deka Jacketed 2 Wire, 10 Gauge, Brake Wire - per Foot

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$3.63

Tekonsha Prodigy P3 Trailer Brake Controller - 1 to 4 Axles - Proportional

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$169.94

Pollak Circuit Breaker - Cycling/Automatic Reset - 30 Amp - Straight Mount Bracket

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Question:

My problem is the brakes do not work very well. I have an Econoline Multi-Max Back Hoe Pro 12 Ton trailer. This trailer has 8 each, twelve inch electric brakes. I have 12 gauge wire running from my battery to the brake controller and then back to the trailer connector. I have adjusted the brake shoes and checked all the magnets. The magnets draw 3 amps. When I disconnected all the magnet wires and I connect a battery to the individual magnet pigtails the brake locks up. But when I re-connected all the magnets and put a battery charger with a battery with 13.2 volts at the trailer plug, the voltage at the magnets ped to 10.2 volts and the brakes will not engage, even though the magnets click. The trailer wiring harness has 14 gauge wire going from the trailer plug to the brakes. Could the 14 gauge trailer wiring be the problem and should I re-wire the trailer with 10-2 duplex wiring? Also should I replace the 12 gauge in my van with 10-2? Thanks Danny Rawinsky

asked by: Daniel R

Expert Reply:

I think you are going in the right direction. I would definitely replace the 14 gauge wire going to the trailer brake magnets with 10 gauge wire or larger. Usually larger than 10 gauge is hard to get into the trailer connector though. I would also replace the 12 gauge wire on the vehicle side. You do not need to remove the existing wire just leave it there and use tape or a zip tie to make sure it does not get in the way on either end. Use 10 gauge wire, item # 10-1-1 for this connection also. You definitely need to replace the wire running from the battery to the brake controller and I would use the same 10 gauge wire for that along with a 30 amp circuit breaker, item # PK54530.

Another thing I would do is make sure that the trailer brakes are all grounded securely with at least 10 gauge wire. If this is the case you can use Jacketed 2 Wire, 10 Gauge, Brake Wire, item # 10-2-1, on the trailer. If the ground on the brakes is running forward to the trailer connector I would eliminate this ground, and ground each of the trailer brake magnets as close as possible to the trailer frame. Make sure that the wiring cannot be cut, pinched, or broken by movement of the suspension. Also make sure the ground wire at the trailer tongue is connected to a substantial part of the frame that is free of paint and rust. If your trailer is a tilting style trailer then the grounds, from the brake magnets, may require that they be ran forward to the trailer connector or grounded at the coupler.

Once you have all of the wiring replaced you should be good to go, but if you experience the same trouble you will need to make sure that the brake controller installed on your vehicle is rated for a trailer with eight brake assemblies. If not you will need to replace the brake controller with one that will handle eight brakes on a trailer. I would recommend the Tekonsha P.3, # 90195, in this case.

expert reply by: Robert G