Does Trailer Wiring Install for 2018 Ram ProMaster City Require Running Wire to Vehicle Battery

Question:

So youre saying that I can use the part #37185 4 pin to 7 pin adapter with no 12v going to the battery with my installed #118719 4 pin wiring harness that has 12v to battery instead of the # ETBC7 that includes a long black 12v wire for the battery.

asked by: Lee S

Expert Reply:

When installing trailer wiring in your 2018 Ram ProMaster City like the # 118719 you do have to run the power wire up to the battery to ensure your vehicle's wiring circuits are totally protected. Otherwise you run risk of damaging the circuit that powers the 12 volt power circuit you mentioned which would kill the trailer lighting and potentially damage the vehicle wiring.

I attached an install video for this kit that shows it installed in a similar 2017 Ram ProMaster as yours that covers running the wire as well.

expert reply by: Jameson C

Lee S.

4/21/2020

Thanks. Another question I have. I'm buying your 4 pin to 7 pin wiring kit that has a 12volt line to the battery. I'm also buying a takonsha proportional brake controller that also has a 12v line going to the battery. So am I correct that this setup requires 2 12v lines to the battery?

Jameson C.

4/21/2020

The setup you mentioned does require running two power wires to the vehicle battery but only the trailer wiring one would run from the back of the vehicle and the brake controller would run from where it mounts in the interior of the vehicle. The 12 volt circuit from the 7-way would not have to be completed from the # ETBC7.

Lee S.

4/21/2020

Jameson C.

4/21/2020

If you don't need the 12 volt accessory circuit on your trailer wiring (it's not needed for a brake controller install) you do not have to run the black wire from the ETBC7 or 37185 to the vehicle battery. You can leave it unconnected. The black wire of the brake controller does need to run to the battery but that would be it.