I'm installing a Westin trailer lights adapter on my 2009 Mini Cooper hatch. I have trailer lights that I'm using to make sure the install is correct. So far I got the left and the right trailer turn signal lights to work. The problem is with running lights and brake lights.

Below is the picture of the driver side rear light connector unplugged on my Mini Cooper. Left trailer light is connected to terminal 6 and works fine.

Trailer running lights work fine from either terminal 2 OR 3.

However, as soon as I connect the trailer brake wire to either terminal 2 or 3 the trailer brake light goes on even when brakes are not applied.

So I can have running lights in terminal 2 and brake lights in 3 and brake lights are on when brakes are not applied. Or I can have running lights in terminal 3 and brake lights in 2 and brake lights are also on when brakes are not applied.

I tried all possible terminals/combinations and brake lights are always on. What am I doing wrong?

The cooper lights work fine by themselves - brake lights come on only when brakes are applied.

Testing with just a test light, both terminals 2 and 3 make the test light light up on low without brakes, and the test light lights up bright when brakes are applied. So seems to work fine with the test light but not when the trailer lights are connected through the Westin adapter.

I feel like it's something easy that I'm missing but I can't figure it out. How can I get the trailer brake lights to come on only when brakes are applied and have running lights always on whenever car lights are on? Please help - this is driving me nuts!

 

Are you saying the trailer has a separate brake circuit? Small trailers usually have combined brake/turn lights.
Don't you have the instructions for the adapter?

Make sure the trailer is properly grounded by the way. The hitch itself isn't always a reliable ground. There should be a wire from the trailer frame to the adapter (usually white), and then the adapter should have a ground to the chassis of the car.

 

Actually I'm starting to suspect a faulty Westin controller/adapter. I disconnected the trailer lights and just tested the controller.

Everything works as it should on the Cooper rear light connector. Terminal 2 and 3 make the tester light light up dim when no brakes are applied and bright when brakes are applied.

Once I install the Westin controller and test the output from the controller, without the trailer lights connected, the Brake wire is always at 12v. The controller is connected exactly as specified in the Westin instructions. I've got good ground. I'm going to call them tomorrow and see what they say.

 

I suspect the "Brake" terminal is for electric brakes, not brake lights.

 

Confirmed that Westin 65-75390 does NOT work on the MINI because it's not compatible with 3-wire systems with combined Stop/Tail light functions. This is despite the fact that the instructions that come with it explicitly state that it is. Ha.. Well, their tech support said that the unit itself is not compatible and they were not sure who wrote the instructions at Westin. Apparently, they only supplied the board and Westin did the packaging and the instructions.

The same tech person told me to buy Curt 56236 unit that should work. I checked and etrailer.com also lists Curt 56236 or 59236 (extra wires) as guaranteed compatible.

What a pain!