Is Breaker Also Needed on Fused Trailer Brake Controller Circuit of Tow Vehicle

Question:

I read Chris Ps question, and Michaels answer, but I have a follow-up question. This, by the way, is valuable information to me, because Im a rookie braked-trailer owner. Similar to Chriss question, I also have a 2005 Ram, and it also has a trailer brake plug under the dash, as well as a dedicated, factory-installed fuse in the fuse panel labeled electric brake. I have installed a brake controller, as well as a 7 pin to four flat adapter plug. I connected the brake control using an aftermarket wiring adapter, and after testing it on my trailer, I discovered that the trailer lights were not working. My main question is this: If I have a dedicated fuse for the controller, do I still need to install a circuit breaker for the 7 pin? Also: Does plugging in the four flat adapter supply the power for the lights? Do I only need to run two wires to the engine compartment, since my trailer does not have backup lights? Awesome site, guys, and I look forward to your answers!

asked by: Mark A

Expert Reply:

If you have a fuse for the brake controller you do not need anymore circuit protection on that specific circuit. So if the breaker you mentioned was for a brake controller output circuit then no you would not need it. If the circuit the relay like # 9510 was going to go on was for the 12 volt accessory circuit which is totally different then yes you would still need that breaker.

Plugging in the 4-way to a 4-way to 7-way adapter does cover all of the trailer taillight circuits. The two wires that run to the engine compartment are the brake output circuit and the 12 volt accessory circuit. You definitely have to run the wire for the brake output circuit but if you don't have a use for the 12 volt accessory circuit it's not needed at all as it's totally independent of the rest of the trailer wiring.

expert reply by: Jameson C