REM not working, going crazy when we connect something to the towsocket
 

My brother's 2000 V70 started acting up when he connected his caravan to the towsocket. The rear wiper is running constantly when the caravan is connected and the reversing lights are lit regardless of what gear the car is in.

If we disconnect the trailer, the rear wiper doesn't work and the reversing lights won't turn on if we put the car in reverse. The rear doors and the hatch also won't lock with the remote (I'm fairly sure this is an indication that the REM isn't working properly). The rear lights, braking lights and license plate lights are all working.

We've tried powercycling the car as described in a different thread here with the same symptoms (though no mention of a towsocket or caravan there) but that didn't work.

We've checked all fuses and none are blown.

Any ideas?

/Raniz