Trailer Lights Not Working on a 2008 Mercedes-Benz GL320 With ModuLite Ultra Protector 119192

Question:

Installed this following the 2010 Mercedes video as the rear compartments are identical to mine. No trailer lights coming off the 7-way, but meter detects power. Tested the 4-way with some temporary magnetic blinkers and blew the fuse?

asked by: Alfred

Expert Reply:

The ModuLite Ultra Protector Wiring Harness w/ Integrated Circuit and Overload Protection # 119192 has a re-settable short circuit and overload protection built in that protects itself and your 2008 Mercedes-Benz GL320 from electrical shorts and mis-wiring problems. This means that it will shut itself off and restart instead of allowing a fuse to blow.

Since you have tested the functions on 7-Way of your GL320 and they seem to all be operating properly the problem is most likely on your trailer. You can verify this by hooking the trailer up to a different vehicle or testing the functions with a separate 12V power source. You will also want to make sure that the connector is clean and free of any debris. Since it sounds like your magnetic blinkers aren't working either you will want to test them as well.

If the problem is on your trailer, then you will want to inspect the ground connections and any wiring from the connector all the way to the lights. Look for any wiring that is bent, damaged, exposed, or corroded. You can replace it using 16 Gauge Wire # DW02359-1 and Butt Connectors # DW05744-5. If the wiring looks good, then you can test it using a Circuit Tester # PTW2993 and use the sharp point to test different sections of wire.

If the functions and wiring on your trailer check out and you are still getting the proper signals on the 7-Way of your GL320 but they are not working together then you will need to take your GL320 and trailer into a qualified mechanic who can physically inspect your setup.

I have also attached some helpful articles about trailer wiring and troubleshooting for you to check out.