Tail Lights Cut Out After Trailer Plugged In on a 2012 Mercedes-Benz Vito

Published 10/22/2018

Question:

Hi I have a vito van 2012 plate iv wired the trailer plug and it all worked fine when I plug my caravan into the van I put on my lights tail lights they come on for around 3 seconds then go out I still have brake lights and indicators and head lights just no tail lights on van or caravan as soon as I unplug the trailer or caravan the light come back on

asked by: Stuart

Expert Reply:

It sounds like you are overloading the tail light circuit on your 2012 Mercedes-Benz Vito. In order to test this you will want to remove a few of the lights hooked up to the tail light circuit and then plug the trailer back in and see if the problem persists. If not then you know you have too much power being drawn for the tail light circuit.

In order to fix this you are going to need to use a powered converter box. This is going to draw power needed for the trailer lights from the battery, not the vehicle lights. For this, I recommend the ZCI Circuit Protected Vehicle Wiring Harness w/ 4-Pole Flat Trailer Connector # 119250KIT (US Only) which allows for a max of 7.5 amps at the tail lights.

If overloading the tail light circuit does not seem to be the issue then the only other thing I can think of is a poor ground. I recommend sanding down and reattaching the ground wire for all of the tail lights and both of the trailer connectors, vehicle side and trailer side.

expert reply by: Conner L