Troubleshooting Trailer Lights Working Erratically on a Trailer Towed by a 2000 Jeep Grand Cherokee

Question:

I have a 2000 jeep grand cherokee. I have a 4 way trailer light kit. I hooked up the wires the way they are marked. I have no brake lights and when I turn the signal light on, with the tail lights, both signal lights work at the same time. Without the tail lights on, the signal lights work fine. The kit did not have a brake wire listed, only turn signals and tail light. The existing trailor has a five wire plug, no electric brake.

asked by: wayne m

Expert Reply:

There are several things you can check. First, check the functions on the vehicle side with no trailer connected. Make sure the wires are receiving the proper signals at the connector on the Jeep. You will need a circuit tester like # PTW2993. If you find a problem at this point, something may not be wired correctly, and you will need to start from scratch. Wire color and functions are usually: white = ground, green = right turn and brake, yellow = left turn and brake, brown = running lights. I have included a video on circuit testing wires below.

If the wiring at the vehicle side 4-Way is not functioning properly, check the signals coming into the powered converter. If the signals going into the powered converter are accurate, but wrong coming out, then the converter is bad and will need to be replaced. If you do not have a powered converter installed on your Jeep, one is required to convert the 3 wire system to a 2 wire system and protect your vehicles sensitive wiring.

The wiring harness specifically for your 2000 Jeep Grand Cherokee is the Curt T-Connector Custom Fit Vehicle Wiring, # C55369. This powered harness connects behind the interior trim panel in the cargo area, on the driver's side. I have included an installation video below. You could then add Adapter 4 Pole to 5 Pole Trailer Wiring Adapter, # 47515, and connect the additional wire to a reverse light wire behind the taillight assembly on your Jeep.

If you want to hardwire your Jeep, you can use Upgraded Taillight Converter, # 119190. This is also a powered converter that requires a direct connection to the vehicle battery. You will need to hardwire the harness by function behind the vehicles taillights. Use a circuit tester to locate the correct wires behind the taillights.

There could also be a faulty ground. Trailer lights usually ground through the mounting studs. Check to make sure the grounds are not dirty, corroded, and are properly attached. A bad ground could cause all sorts of malfunctions. I have included a video below on testing for a ground below.