Troubleshooting Potential Overload on Curt Wiring Harness for Taillights Not Working

Question:

I believe my new trailers tail and side lights slightly exceed the Curt C55567s 6-A rating. These lights never came on. I thought the C55567 has overload protection on all circuits. Investigating, Ive verified that the voltage of this output brown wire s from 12 V to 7.5 V when a single LED bulb normally ~40 mA at 12 V is connected, and it illuminates the LED bulb only dimly. Connect a single 5W incandescent bulb and nothing happens, except that the voltage s to virtually zero 5 mV. Do you think my C55567 converter is toast? Do you see failures like this often? This hardware was installed by my Toyota dealer. The brake and turn signal lights work okay. Thanks.

asked by: Chris

Expert Reply:

If the draw of your taillights and side clearance lights combined exceeds the 6 amp maximum, it is quite possible the converter box did short circuit. Short circuiting at the box is the way the harness protects from overload.

It is also important to note that the harness' 12V power wire must be connected directly to the vehicle's battery, through the supplied fuse holder, not to an auxiliary 12V power source elsewhere on the car.

If you find that the taillights and clearance lights are drawing more than 6 amps, you will want a heavy-duty wiring harness, like the Tekonsha ZCI Circuit Protected Wiring Installation Kit # 119250KIT. This wiring harness will allow a max draw of 7.5 amps for the taillights.

expert reply by: Victoria B

Chad H.

7/27/2020

I recently purchased a slightly used boat trailer.. and i brought it home .. it had what appeared to be relatively new non-submersible lights on it.. about halfway back home.. i realized the lights were not working on the trailer.. so i unplugged it.. after checking the trailer out.. i had to replace all the wiring (dry rot) and the lights which were not working at all. I replaced the lights with submersible LED.. which had a tester along with it.. so i knew they worked.. i then hooked it all up .. and still notta.. so I rigged another 4 pole connector to a 7ah 12v battery .. and plugged in group.. then tested Green- (good) yellow (also good) and brown (both lights came on).. so now i know the trailer is good hitch to stern.. which means my harness got toased .. i think>? is there a reset on the module or do i just need to buy a new harnesS?

Chris R.

8/2/2020

It definitely sounds like a bad harness/module on the vehicle side. If that's the case there's unfortunately not a reset switch built in so you will just need to replace the module and harness itself. If you can tell me what model vehicle you have I would be happy to make a specific recommendation.