Is Power on Stop/Turn Circuits of Curt Trailer Wiring Mean Problem with Converter Box

Updated 01/21/2026 | Published 01/20/2026

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness for Factory Tow Package - 7-Way Trailer Connector

(56)

$86.04

Hook Probe Circuit Tester

(66)

$13.78

Question:

I purchased a curt 4 pin wiring harness for my 2018 Jeep wrangler JL a few years back and i just plugged in my utility trailer and the brake lights came on before i started the vehicle. When i test the plug on the Jeep it shows power coming down both left and right directional. The running lights work correctly but no directionals only constant brake light. Is this a problem with the converter? worked fine for years Gratefully, Luke

asked by: Luke R

Expert Reply:

Hey Luke, yes this is typically indicative of a problem with the Curt trailer wiring harness you installed. To test this for sure you would want to use a circuit tester like the part # PTW2993 to test for voltage on the input side of the converter box on the circuits that are hot all the time. If there's no voltage on the input side of the box but there is on the output side of the stop/turn circuits then the box is bad and needs to be replaced. If there is voltage then the problem is not the box and something to do with wiring up further on the vehicle.

expert reply by: Jameson C

Luke R.

1/21/2026

Thanks so much, I'll get that done. One other question if i may. Is the converter box replaceable without having to buy the whole kit. If so, what is the part number? I had purchased part # 56407 originally Gratefully, Luke