Anyone use X5 to put a boat in water?
 

I have an 03 X5 with an e-trailer hitch and wiring harness. I installed both several years ago and have never had an issue. We have a new boat trailer that automatically applies the trailer brakes when the trailer is not plugged in to the tow vehicle. If it is plugged in then the brakes are not engaged when it goes in to reverse.

Today was the first time using it. We hooked up to the trailer (boat off and in water) and it worked great ie brakes not applied on trailer when in reverse but unplugged and in reverse trailer brakes are applied. We took the boat out of the water to go gas it up and then put the boat back in the water. The launch worked great, no issues. After we put the boat in the brakes on the trailer kept engaging when I would put the car in reverse indicating the trailer harness does not recognize it is plugged in.

The wiring harness did get wet when we put the boat back in the water. Thinking it might have been a blown fuse I checked all fuses that I thought it might be but did not find any. The lights seem to be working correctly on the trailer. I checked the tow vehicle wiring harness with a test light and did not have a hot wire but when the lights or brakes are applied I had power.

Anyone have any ideas on what might cause the brakes to engage on the trailer while the trailer is plugged in and tow vehicle in reverse?

I would expect that the hot wire in the plug keeps the brakes off in reverse. That is the fuse you need to find. It is likely part of the trailer installation wiring.

My trailer uses a solenoid valve to block the hydraulic disc brake when reverse is engaged. Long as the reverse switch is working (and the lights come on), all's good.

JCL, I suspect you have nailed it as that is what I thin is going on because with a test light I do not have a hot wire working.

I installed the wiring harness years ago and my memory is not so good. It seems all I did was splice in to the left rear tail light harness. Do you have any idea what fuse I need to track down? Would it be in the fuse box in the glove box, or the one in the right rear quarter panel? Or is there another place to look?

Thanks in advance for any insight.

On most trailers the electronic lock-out is tied to the reverse lights on the vehicle. The idea is that if you were on a hill and the rig started to roll backwards, the trailer brakes would stop it...when the reverse lights are on the solenoid releases the trailer brakes as it "knows" you mean to go backwards. One of the four hot "pins" on the connection needs to be connected to the reverse lights on the SUV. Check the fuses/relays for reverse lights.

Thanks X-cellent, I will recheck and see if I can find it. It was working great until I backed up just enough to get the entire plug wet, that is why I suspect it was a fuse. Do you know if there is another fuse panel besides the one in the glove box and right rear quarter?

Check to see if there is an inline fuse in the trailer connection, ie not part of the BMW fuse panels.

Not sure if it's related but my connections on my wiring adapter weren't secure so when it was plugged in, some lights weren't recognized. I had to replace the adapter and things worked fine (note: I didn't have a trailer with brakes)

these things...
Curt Wiring Adapters : Cabela's

JCL,
Good point! When I installed it several years ago I did not remember there being a fuseable link in the harness. I will take a look and see. I need to do some trouble shooting and figure out what is going on.

I can put the trailer in with out it simply by putting a special tool (or a nickell) in the slide mechanism on the trailer.

A thread on towing boats, hitches, et al...
may be of help.

Also, there was a thread a few months ago that initially showed a pair of white Xs putting their boats in the water via a steep boat ramp; that OP may have some good info too, though a quick search did not turn up the recognizable thread.
GL, mD

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