Broken wire syndrome, wiper could well still park! also check that No plate lamps are still working. Pull the rubber sheathing back, and have a proper look, and also give the wires a tug, just incase the wire may have broken inside its own plastic coating...
If you find broken wires, don't just solder them back together, add a new 8 inch piece in, so you can tuck the wire back into the roof, and leave brand new wire, where it is most vulnerable to break again... should last another 20 years

Thom