Location of 12-volt Power Feed To Trailer Fuse on 2015 Ram 3500

Question:

What is the location for the fuse that charges the battery on my fifth wheel? Thank you

asked by: Bill A

Expert Reply:

The fuse for the 12-volt accessory circuit feed to the 7-way is a 30 amp fuse in location F30 in the fuse box in the engine compartment.

Keep in mind that due to the distance between the alternator on the tow vehicle from the trailer battery and the small wire gauge used in that circuit limits the amount of amperage that can be delivered on that circuit. You can maintain a battery but there won't be enough available amperage to charge a depleted trailer battery.

If shore power is available, you can use a battery charger like # CTEK56353 to completely charge the battery. Another alternative would be to use a DC to DC battery charger like the Redarc # RED46FR to completely charge the trailer battery using the tow vehicle's alternator as long as the vehicle is running.

expert reply by: Mike L

John P.

3/18/2024

is the wiring for the trailer 12v aux line hooked up from factory on the 2015 dodge ram 3500? On my GMC Yukon it was tucked in near the batter tray but I had to hook it up.

Mike L.

3/19/2024

@JohnP As long as the truck came with the OEM 7-way trailer connector, and the fuse in location F30 is in place, the 12V circuit will be active.

Paul T.

3/12/2025

Hey Mike L, I have checked the fuse (F30) and also swapped it out just in case, still have no power at the back of my truck. I disconnected the plug on the back of the 7 way and there is no power there either. I tried to follow the wiring up the frame in case there was another plug somewhere else, but lost it in the mass of wires. Is there also a relay that controls the 12 volt power? I am about to run another wire if I cannot get this figured out. While I know the power isn't great when it is functioning correctly, it is still nice to have it charging while driving down the road. Paul