The fault I was experiencing was the wiper wouldn't park and when turning off the wiper at the switch it would just stop at any position. John H gave me a bit of advice and I replaced the unit with a spare one which worked perfectly so thought I would take the faulty one appart and this is what I found...

(excuse the quality of the pics)

I removed the 5x7mm screws to find that it was full of water (pic 1) but realised quickly that this gave access to the gearing so didn't have to open it at all, but gave me the oppertunity to dry it out & regrease the gearing.

Next I removed the little 4.5mm screw and slid out the connector block (pic 2) due to the water the contact was very rusty so gave the contacts a clean (pic 3) and re-tried the motor but the same fault was still there i.e. as soon as the switch was turned off the spindle stopped in whatever position.

I therefore re-oppened the connector block and noticed on the back of the large gear wheel (Pic 1) (the big rusty cloured one to the left) was a lug about 1" in length this is designed to seperate the contacts (pic 3) but wasn't I therefore bent the middle of the long metal piece of the contact in direction of arrow (pic 4) re-assembled it and again tried and this time it worked perfect so I again have a spare motor

Alan, this is great.

Pleasure