Trailer Turn Signals Flash Very Dim and Show Inconsistent Voltage

Updated 09/30/2011 | Published 09/29/2011

Question:

Is it normal for the voltage to flash in a sequence of 2, 7, 11, 12, 12, volts with the turn signal on? Or should it just be reading 0, 12, 0 12, 0, 12 volts continuously? Im confused because I have a brand new trailer that seems isnt getting enough power to the lights. I have 2 trailers and both just have the basic lights. The turn signals flash very, very dim. Its not a ground. I know that for sure. Please help!!!!

asked by: Ian

Expert Reply:

First, I would not immediately dismiss a bad ground simply because there are so many of them in an electrical system that could be faulty. While there may be some fluctuation in the voltage when the turn signal is cycling on and off, it seems like the problem you are having is different than that.

There is an easy way to determine where the problem is. With a trailer disconnected, check the voltage on the turn signals at the vehicle side trailer connector. If they are weak there you know the problem is on the vehicle side. If the signals are fine, then you know the issue is on the trailer.

If you determine the issue to be on the vehicle side the first thing I would check is the main ground wire and make sure it is attached to a clean bare metal surface. I would also look for any nicks or breaks in the wire. From there, you could trace the wires testing periodically for a possible break or loose connection.

If the issue appears to be on the trailer, the first thing I would check is the main ground on the trailer plug. It should also be attached to a clean bare metal surface on the trailer frame. From there, you can also check the wiring for breaks and loose connections back to the tail lights.

Finally, if the lights ground through the mounting studs, make sure they are attached to a clean bare metal surface. A plastic license plate holder can cause this sort of problem as well. If the new trailer has a painted frame, the paint can be causing a bad ground.

Also check the vehicle side and trailer side connectors for any dirt or corrosion and clean them out.

expert reply by: Michael H