Trailer Lights Wont Work with Headlights On

Published 09/12/2018

Question:

I have a 1994 Toyota pickup. Some years ago I had a Hoppy electronic taillight converter, #310-0041-560 installed. I have only towed a friends 4-pin trailer a couple of times in daylight. The stop and turn signals work fine during daylight. I thought the tail lights for night use also worked but never really tried them until recently. If the truck lights are turned on, none of the trailer lights function, but if the truck lights are turned off, the turn and brake lights on the trailer work fine. I cleaned and checked the ground, so that is not the problem. Did the mechanic I had install the converter pick a converter incompatible with Toyota wiring? A search of your site turned up part #C55379 that says that it is compatible with my truck and will give me a functional 4-pin trailer connection. Do I need to ditch the Hoppy converter and purchase yours? Thank you,

asked by: William

Expert Reply:

When we have customers tell us that their trailer lights only work when the vehicle's headlights are off then this is usually a ground issue. Did you check both the trailer side and vehicle side connector? If not I would do this first and also, by check I mean you should remove each of them, sand down the surface and then reattach with new mounting hardware. A visual inspection of the ground terminal is not sufficient to check for function.

The other potential cause is that the lights are drawing too much power from the vehicle but this would usually cause a few blown fuses. If you unplug some of the lights you would be able to rule this out. I don't think the issue is with the converter box but rather the wiring. The Hoppy Taillight Converter part 310-0041-560 is universal so compatibility is not the issue either.

The Curt T-Connector Vehicle Wiring Harness part # C55513 is indeed a confirmed fit for your 1994 Toyota Pickup and may be an option if all else fails.

expert reply by: Conner L