Trailer Brakes Instantly Apply When Trailer is Plugged Into Tow Vehicle

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Question:

I have a 2009 Toyota Tacoma with trailer towing package. It came with a trailer wiring harness that plugged into the vehicle and then I connected to my brake controller. The truck came with a 7 pole trailer connector, but my horse trailer only has a 5 pole wiring end, so I bought an adapter to connect the two. Lights, turn signals seem to work fine, but trailer brakes lock up as soon as I connect the trailer end to the truck end.Disconnect the trailer wiring and the wheels move fine. Instructions with brake controller say the problem is caused by incorrect location of connection with vehicle stoplight wire tapped to hot side of stoplight switch instead of cold side, but this is a factory plug in harness, so how could that happen?

asked by: Eddie C

0

Expert Reply:

Are you sure that the horse trailer has a 5-Way connector, and not a 6-Way such as part # 30205?

In any event, I do not believe this is a problem with your brake controller. I would bet that the adapter or the trailer is wired incorrectly. When the adapter is plugged in, the pin for the trailer brakes is contacting the pin for the 12 volt accessory lead on the 7-Way connector on your Tacoma. As soon as the trailer is plugged in, the brakes instantly receive 12 Volts, and lock up.

There are two accepted methods of wiring a 6-way trailer connector. One uses the center pin as the brake output, the other uses the center pin as the 12 Volt accessory lead. If the adapter is wired one way and the trailer the other, you will experience the problem you are describing. If this is indeed the case simply rewire the adapter, swapping the 12 Volt pin and the brake output pin.

If your adapter cannot be rewired you can use the Adapter 7 Pole to 6 Pole - Universal, item # 47549, which can be rewired for your trailer wiring configuration.

If you look at the photo I've provided, it'll show you how your brake controller wiring harness should be pinned out. Examine the plug on your harness, and compare it to the photo to ensure everything's pinned out the way it should be.

expert reply by: Mike L

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Trailer Brakes Instantly Apply When Trailer is Plugged Into Tow Vehicle

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