ORIGINAL: zcacogp
Ian,
I would have thought a replacement relay would be a good start to experiment with. It may be a little different, as the Golf (Mk1, 2 and 3) arrangement has a stalk on the RHS of the steering wheel, and pushing it forwards turned the rear wiper on. The stalk sprung back if you did this (i.e. it didn't stay forwards), and you pushed it forwards again to turn the rear wiper off.
This would suggest that the VW rear wiper relay turns on with a single pulse, and turns off with a single pulse as well. If you fitted one to a 944 you may find that this would give the same behaviour - you would need to switch the console switch on and then off to turn the wiper on, and then turn the switch on and then off again to turn it off. Hence a replacement switch may be an idea (either a sprung rocker or a push-button.)
Oli.