Found this:
Had exactly the same problem on my son's Corsa C. Wipers don't park on intermittent. Checked the wiring / relays out. Easiest way to check this out without having to open the body control module is at the wiper motor connector where it goes onto the motor. This is a five pin connector labelled A through to E. A is the yellow wire nearest to the offside of the car, and the others follow on in order. The important one to check for self parking is pin D. This should have a permanent +12V feed. If it has, (as ours did), it proves the wiring and relays are OK. Next I removed the motor / linkage assembly. Once this is off the car, there are three small torx headed screws on the motor case. Remove these and carefully and evenly prise off the cover plate. There are several plastic rivets also holding this but they will release if you are careful. Inside the cover plate you will see three copper fingers. The self park circuit is controlled by the two furthest from the centre of the motor. What happens is these fingers lose their tension and don't make a reliable connection with the round disc below. You may even spot signs of arcing, (a black deposit), on the cover plate just above the outermost contact. On the circular metal disc, on the outer edge will be a notch which is infilled with a nylon piece, (you may need to clear away the grease to see fully). On our motor there was a burn mark where the contact had been arcing. Clean this away. Carefully bend the copper fingers down away from the plate so that they now make a reliable connection on the circular disc when the cover is replaced. Repack with grease and if required use a sealant such as hylomar before replacing the cover plate and the screws. Refit the motor and linkage and you should be in business!
http://www.allcorsa.co.uk/forums/showthread.php/windscreen-wiper-problem-25736.html?s=e4b8991e99422b5fabd47c2b21f9dfa0&