Troubleshooting Trailer Wiring on a 2015 Ford Transit T350

Published 12/09/2015

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(205)

$67.35

Adapter 4-Pole to 7-Pole and 4-Pole

(648)

$59.13

Hook Probe Circuit Tester

(58)

$12.11

Question:

2015 Ford Transit 350. No factory trailer light/brake wiring. Tekonsha Prodigy P2 brake controller already installed. Can the wiring adapter be used with a 7-pole plug by cutting off the flat 4-pole and matching the wires to the appropriate terminals in the 7-pole plug? I tried a traditional splice into the existing tail light wires method of wiring trailer lights and Im getting an error message in the van when I hook up the trailer. It seems the additional load from the running lights/brake lights/turn signals on the trailer make the vans electrical system think somethings wrong. Trailer brakes work just fine. Doesnt blow any fuses or anything. Just the brake lights/turn signals dont work when the trailers hooked up but work again once the trailer is disconnected. Does the power booster included in the wiring adapter eliminate this problem?

asked by: Lyle S

Expert Reply:

I can help you troubleshoot your wiring issue.

You are correct when you say that you will need the power converter that is used by the Curt harness # C56249 you referenced. This will have a 12 volt wire run to the battery and will allow all your trailers functions to work properly. The converter will draw the power from your vehicles battery instead of the taillights which sounds like is the issue you're having.

Yes, the wiring adapter # C56327 can be used on the 7-way if you cut off the 4-pole end. It is important to note that once you cut off the 4-pole it will void the warranty of the harness. You may want to check the functions with a circuit tester like # PTW2993 to make sure the harness is functioning properly before you cut off the 4-pole. We typically recommend using a 4-way to 7-way adapter like # 37185 to prevent having to cut off the 4-way end.

expert reply by: Jackie C