Where to Install Diodes of Tow Bar Wiring on Vehicle with Aftermarket T-One Style Trailer Wiring

Published 12/10/2019

Products Featured in This Question

Roadmaster 4-Diode Universal Wiring Kit for Towed Vehicles - 7-Way to 6-Way Coiled Adapter Cord

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2.5-Watt Solar Battery Charger

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Question:

Thanks! I have the car apart while I am working it up, including the battery out. I used a jump starter to apply power to the trailer ground and the three lights connectors and experienced something odd: some car systems powered up! The entry lights came on and something began whirring. This may be the power booster back feeding... This has me concerned because this car requires a battery disconnect during tow. If I connect before the trailer package light booster isn't this still a possibility? Are the diodes to prevent power from traversing up into the car systems? Can you tell me which color on the trailer system T connection corresponds to which light type? Driver's side has brown and yellow which seems like that brown would be tail light and yellow would be brake and turn. The passenger side has green and red...

asked by: KevinC

Expert Reply:

It would be nice if you could plug your trailer wiring into your tow bar lighting 4-way and be set, but the trailer wiring 4-ways are designed to be used in reverse so the lights of the vehicle would not light up.

So what you'll need to do is install the diodes of the # RM-15267 before the 4-way connectors and the tow bar lighting will work just fine. Technically the trailer wiring would be active when the tow bar lighting is, but since you wouldn't have anything connected to it this would not cause any additional draw or adverse reactions!

expert reply by: Jameson C

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Kevinc

12/10/2019

Jameson C.

12/10/2019

Applying power to the trailer's ground wire isn't recommended as that will cause a short and possibly melt some wiring. Hopefully this didn't damage anything on your vehicle/trailer. With the vehicle battery disconnected when you are flat towing there wouldn't be anything that would put power on the ground circuit so the circuits that activated like you mentioned would not happen again. The diodes of the lighting kit prevent voltage from backfeeding onto the vehicle wiring as well as that's one of their primary functions. The tow bar lighting voltage will only be able to make it to the taillight of the vehicle. We don't have a way to look up the wiring colors of your taillight wiring but what you can do is use a circuit tester like the # PTW2997 and probe all of the wiring till you find the correct wiring to use.