Troubleshooting a Modulite Wiring Harness on a 1990 Toyota 4Runner

Question:

I have a Draw-tite modulite trailer light power module Part 18187 I believe not working. I tested the right turn signal going into the power module and have power but not coming out of the power module. The brown wire for the running light work.

asked by: Daryle

Expert Reply:

You started at the right place. If you have power going into the converter on a brake or turn signal circuit and none coming out on the trailer side then the modulite has gone bad or has been shorted out. The taillight circuit does not require conversion so it usually will work even if the converter is shorted. The taillight circuit working shows the ground connection is good.

I would check the trailer wiring out, before reconnecting it to a new wiring harness on the vehicle, to make sure there is not a short on the trailer that caused the modulite on your vehicle to go bad.

We now recommend the 4 Pole Trailer Connector, item # C59496, for your 1990 Toyota 4Runner. This wiring harness protects your vehicles sensitive wiring from possible mis-wire situations or shorts in the trailer wiring.

expert reply by: Robert G