Can Trailer Wiring Harness 12 Volt Power Wire be Connected to Trailer Battery

Question:

Once the harness is installed, does it need to be connected to the battery when its not attached to the trailer? Instead of attaching to the car battery, I have a battery on the trailer I could attach it to when I was towing it, and store it when not in use.

asked by: Alana L

Expert Reply:

A powered trailer wiring harness such as # C56165 will be permanently connected to the vehicle battery. It cannot be connected to any other 12 volt source. A battery on a trailer would be a bad place to connect the 12 volt wire because for 1 reason the car battery is charged by the alternator. A trailer mounted battery at best can only receive a maintenance charge from the vehicle.

I have included a link to a help article with tips on routing the power wire for you.

For your 2008 Toyota RAV4 the wiring harness I would use if it were me is # 118412. They have proven to be the more reliable choice.

expert reply by: Michael H