Trailer LED Tail Lights Light Up Dim When Connected to Vehicle with Curt Trailer Wiring Harness

Question:

I am having a problem with the wiring harness I bought curt #C56378. I have LED tail lights on my trailer and noticed as soon as I plug in the connector, the trailer taillight LEDs light up very dim with the vehicle off and no taillights activated. When activating turn and stop lamps they function as intended. When plugging into a trailer with incandescent bulbs, there is no problem. They do not light up dim. This unit is powered with circuit protection. Is there a reason the LED lights come on dim when plugged in?

asked by: Pat

Expert Reply:

Curt trailer wiring harnesses like # C56378 sometimes have the exact issue that you are describing. The issue is that there is some bleed over power from the powered converter that can light up LED lights ever so slightly. This is usually not an issue because at night you would have the running lights on any way and during the day it should not be all that visible.

The reason that it happens with LED lights and not incandescent lights is that the LED lights draw much less power to light up so the small amount that is coming through is just enough to light LEDs up dim. Incandescent draw much more power so there is more resistance and the small amount of power is not enough to light the bulbs.

If you want to stop this completely you could install load resistors # DI34ZR, one on each affected circuit, to create more load so the lights will not light up when they should not be.

My contact at Curt stated that the small amount of power will not drain the vehicle battery since it is much a minute amount of power. You can also just unplug the trailer from the tow vehicle when parked if you are worried about draining the battery.

expert reply by: Michael H