A common problem on 240 estates (wagons) is breakdown of the wiring to the rear lights and heated rear screen due to bad design. The wiring runs around the hinge on the tailgate and eventually wears through.
This is a clear, easy to follow write-up on how to repair/replace the wiring if it does happen to you.
“I found the wiring harness for the gate at IPD, but opted to perform the repair myself without the harness. The connectors were still in place, so I just cut the wires in the appropriate places and patched them with new wire.
I figured I would have to run the new electric wire through the hinges and behind the tailgate with the assistance of a long, thin piece of non-electric wire. This worked to some degree, though it was rather difficult getting everything through. It took a couple of hours, but eventually I managed to get the upper/center brake light and the defrost wires through. On test, however, I was having some problems: the brake light didn’t work, and the defrost only seemed to work by way of a voltmeter. The dash lit up like a Christmas tree when stepping on the brake. I knew that some of the wire had gotten torn in the process, and knew that I was going about things the wrong way. I tested the upper/center brake light bulb at the chassis of the car not directly connected to the tailgate, and saw that it lit up. I knew I had a ground problem.”