Curt Wiring Harness C56218 Acting Weird After Installing On 2018 Ford Transit Connect  

Question:

Expert Reply:

Hi Charles!

Sorry to hear the Curt # C56218 is acting up, but I can definitely help with that.

First, make sure all the plugs are fully seated and snapped together. That probably isn't the cause, but it is a good thing to double check.

Second, make sure your ground is on a good and clean metal surface that isn't aluminum (which can be somewhat of a problem these days). Also make sure the ground isn't "stacked" with other grounds. It's always best for each ground to have it's own source.

If those are good, it does get slightly more complicated, but not overly difficult. You will need to use a multimeter to test the wires going into the black box for function, and then coming out to make sure that function is working properly. If they are not doing what they are supposed to, you got a defective one, unfortunately. This doesn't happen very often though, so it is most likely your ground that is causing the problem.

Either way, let me know if that does get it working properly or not.

What are you going to be towing?

expert reply by: Lazer S

0

Charles C.

11/3/2026

ok will try moving the ground. It is on with an existing ground connection. Did not have time to look at it today. i have a meter and I am very well versed in 12volt systems. I had tested it with a meter before I picked up the trailer. It seemed to work correctly then. Running light pin had 12.8, blinker pins "blinked". Now they don't read correctly with meter. The ground sounds like a logical first step. Trailer is a small utility trailer. Not an urgent fix but will need it for taking leaves to the dump soon. Installed the Curt hitch. That was a breeze! I'll let you know what happens Chuck