Factory 30 Amp Fuse for Trailer Brake Control vs Auto Resetting Fuse on a Ford F-150

Updated 04/08/2013 | Published 04/04/2013

Question:

I have a ford f150 that is factory pre-wired for towing with the jumper harness F85Z-14A348-A under the dash that connects to a controller and the trailer tow harness XL3Z-13A576-A at the rear bumper. It seems all the controllers require a 20 or 30 amp breaker. With the factor tow harness already installed and according to the owners manual it has a 30 amp maxi fuse at fuse/relay location #108 labeled Trailer Tow Electric Brake. Is this ok or do they require a auto reset breaker ? Also the wire that feeds the trailer connector does not appear to be more than 14 gage. Is this large enough ? Depending on where I look or what I read some are as large as 8 gage. I will be towing a 24, 4000lbs trailer with two axels. Not sure what size drums but the tires are 13. Could you also recommend a controller for this application. Thank you for your time

asked by: Joe

Expert Reply:

Having the factory fuse is perfectly fine for an aftermarket brake controller. The benefit of a circuit breaker is that it can reset itself so you do not have to replace a fuse should it blow. So you are good to go with the 30 amp factory fuse installed.

If the 14 gauge wire is output to the trailer brakes or even if it is 12 volt power to the trailer connector, 14 gauge is small. I would use 10 for 12 volt power to the connector and 12 for the brakes. However, gauge is determined by the actual copper strands inside and not the overall diameter of the insulation. The wiring could just have a thinner layer of insulation and still be the proper gauge on the inside. I would not go larger than 10. The larger the gauge the more resistance there will be.

For a brake controller I recommend the Tekonsha P2, # 90885. This controller is easy to set up, easy to use, and very reliable. I have included a link to the installation details for it. Since you will be using your factory harness you will need to connect it to the controller by function. On the controller, white is ground, black is 12 volt power, blue is output to the trailer brakes, and red is input from the brake switch.

expert reply by: Michael H