Diagnosing Trailer Jack That Will Not Operate Through Vehicles 7 Way Wiring

Question:

My electric tongue jack used to work when my 2002 chevy avalanches motor was running and the wiring harness was plugged in. Now it does not. I have checked every fuse. Lights on my trailer still work and the jack works on shore power. Any ideas?

asked by: Rick

Expert Reply:

Since all fuses are good and your jack works with shore power, it sounds the 12v from your vehicle's 7 way trailer connector is not reaching your jack's motor. I would start by making sure your aux 12v pin on the vehicle's 7 way connector is showing 12v; use a tester like LCD Digital Circuit Tester # PTW2992. If it is not getting 12v then trace that circuit on your vehicle to check for any cracked or broken wires and also double check the fuses. If you are getting 12v on that pin then use the tester to check the 12v wire going from the 7 way to the trailer's jack while also checking any switch or other item in the wiring. You trailer's lights are working, but you should still verify that the grounds are good as faulty ground connections can cause issues on systems that require more power such as your jack's motor.

You may end up needing to rewire that circuit on your vehicle or trailer with 10 Gauge Primary Wire - Blue - per Foot # 10-1-1 so that it has a fresh circuit to power the jack from your vehicle. I attached a pinout for a 7 way connector along with a demonstration video to help you out.

expert reply by: Andrew N