MINI Cooper DIY – Wiring for a Trailer

In a quest to make my MINI Cooper The Ultimate Hauling Machine I’ve added a tow hitch last fall. Six months later and I’ve only been using it as a bumper protector, leaving the draw bar in with a metal ball protruding out back. It certainly helps to prevent bumper scratches when parallel parked downtown. But that’s not why I added a tow hitch. I wanted to be able to tow a lightweight trailer. To do that I still needed two things – a trailer and a converter kit to make the trailer lights work with the MINI.

I decided to get a 4’x8’ Heavy Duty folding trailer from Harbor Freight. After reading a ton of reviews online it seemed to fit the bill. First of all, it’s light. That’s a key consideration if you are considering towing with a MINI. It’s also easy to move around by hand.

Most importantly, I wanted a folding trailer so that I can put it against a wall and still be able to park both cars in the garage. Keeping it indoors should greatly prolong it’s usable life. That’s good because I paid extra for a permanent tag so that I never have to deal with trailer registration and fees ever again.

Putting the trailer together is pretty straight forward. The included instructions are actually decent.  

Be careful when you’re adding the lights and the wiring. The instructions leave much to be desired here. I ended up slicing the wires in a couple of places during the first folding attempt. I’d recommend folding the trailer first and then wiring so that you can identify any potential pinch spots.

I’d allocate a full weekend to putting the trailer together including the lights. It actually took me longer than that, but I had to step away a couple of times out of frustration.

The next step was to figure out how to wire up the car for the trailer lights. Since I couldn’t find a decent DIY I decided to put one together.


DIY Guide for Installing a Taillight Converter in a R56 MINI Cooper

First step – get this converter from Curt. Ignore this message if it pops up – it fits!

I bought a similar model from Westin and that did not work. I spent hours troubleshooting the Westin converter because everything I read said that it should work on the MINI. Well, it didn’t. After finally speaking to someone at Westin who knew anything they told me I needed that specific model from Curt.

Next – get this wiring kit to hardwire the converter to the car battery. Don’t try to tap a random hot wire to power the converter like I did at first! Seems like it should work, but you’re asking for trouble. I know that the cigarette lighter is right there, but just don’t!

It would be good to have a nice electrical kit handy or you might have everything you need in your toolbox. I ended up using a bunch of terminals, butt connectors, heat shrink, zip ties and a soldering iron – mostly for installing the trailer lights.   

With everything assembled it’s time to begin the install. Take off a plastic cover that hides the latch mechanism. Remove the access panel and disconnect a wiring harness that goes to the passenger side rear light. Run the long green wire from the converter to the passenger side rear light access panel cavity:

Splice the green wire from the converter to the wire sitting all by itself in the rear light wiring harness – that’s the right turn wire. Double check that it’s the same on your car. My MINI Cooper is a 2009 R56 model. The easiest way to check is to use one of these test lights – connect the alligator clip to a good ground, turn the right blinker on from the car and then use the probe to see which terminal makes the tester light blink together with the rear blinker on the MINI.

Here is what testing the terminals with a test light looks like:

With the green wire from the converter spliced into the right turn wire we can move over to the driver side.

Pull the wiring harness on the left side and it will look like this:

Splice the yellow wire from the converter to the wire sitting all by itself in the rear light wiring harness – that’s the left turn wire. In the picture above it’s the one labeled 6.

Splice the red wire from the converter to the wire labeled 2 on the picture above.

Attach the white and the brown wires from the converter to a good ground. This is very important! Here is where I grounded the wires after sanding the spot to bare metal:

Now we need to connect the converter box to the car battery.  Use a car jack and put the car up on jack stands so that the two rear tires are off the ground:

From under the car, feed the long black wire that will go to the front of the car through the existing hole under the tool kit in the boot:

Connect the long black wire to the short black wire on the converter box. I used heat shrink over the butt connector for a secure connection. By the way, a pair of these self-adjusting wire strippers in the picture below should be in everyone’s toolbox – it’s one of my favorite tools.

Working under the car, figure out the best way to get the black wire to the front while keeping it away from any moving parts and the heat. Use zip ties to keep it neat. This picture shows how I routed the wire in the back. I continued following those existing lines to the front.

Take the battery out and you should see an existing drain that can be used to fish the wire up for a neat look.  This picture shows the drain opening (arrow) with the rubber grommet removed (circled):

Fish the wire up through the hole and the rubber grommet:

Connect the wire to the battery. I had to cut the factory red cover on the side a bit to make the additional wire fit:

Connect the trailer and test the lights!

Things I wish I knew before beginning this project:

  • Test the converter box functionality by connecting it to a trailer with working lights. What I mean is, do not try to do what I did and test the functionality of the converter by connecting it to a set of trailer lights that are not installed on the trailer. I wasted a lot of time trying to troubleshoot the converter connection to the MINI not realizing that the problem was with the trailer lights. I thought I had them grounded correctly when in fact they were not. So build the trailer first, install the lights on it and then connect it to the converter’s flat wire. If the lights are not working correctly, connect the trailer to a friend’s truck and see if you have the same problem first, before blaming the connector. If you followed the converter instructions in this post you should not have any issues with the converter connection to the MINI.

I doubt I’m the only one crazy enough to wanna do some light towing with my MINI Cooper. I’ve seen pictures of other MINI Cooper’s towing a trailer so I know for a fact they are out there.

If you were thinking about towing with your MINI but didn’t know where to start, I hope you found this and my other MINI Cooper posts helpful.

Owning a MINI makes sense 95% of the time. For the other 5% just get a trailer!

Click here for other posts on this site that mention the MINI Cooper.

Click here for a list of tools I recommend for DIY auto repair.

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