Installing 4-Pole/7-Way Trailer Connector on Newmar Motorhome

Updated 03/04/2013 | Published 02/28/2013

Question:

I recently bought a Newmar motorhome which came with a 7 pin flat plug. I have a car dolly, also with a 7 pin flat plug. I also bought magnetic tow lights to put on the trunk of the towed vehicle. These have a 4 pin plug. How do I attach both. Is there an adapter that retains the 7 pin plug and adds a 4 pin plug, so I can use both?

asked by: Bob

Expert Reply:

There is not an off-the-shelf adapter that would convert your existing 7-way flat blade to a 7-way and 4-pole, but there are some fairly easy options for adding a 4-pole.

You can access the wiring harness leading to the existing 7-way, and tap in a 4-pole harness like part # 18252, which would allow you to use both harnesses simultaneously. The connector includes a circuit tester which would help identify which circuit serves which lighting function.

Another option would be to completely remove your existing 7-way and install a 7-way/4-pole connector like part # HM48470. If you take a look at our wiring FAQ article, you can see how a 7-way is wired. Be sure to wire by function using a circuit tester rather than wire color.

I have linked you to an install video that will help you through the install process. Keep in mind that you will want to use a tester to verify the function of the wires on the RV.

expert reply by: Mike L