Power steering failing in wet weather

There was the same fault with the Ford Galaxy years ago and this is what was causing it then .




Ford Galaxy upto 2000

Problem: Power steering belt slips in wet conditions.

Solution: The probable cause is water spray passing through the towing eye opening or gap between the undershield and side member. This spray may cause the accessory belt to slip. First, the belt should be checked for tension and wear. Secondly, the engine undershield should be checked for correct seating and adjusted as necessary. Thirdly, the towing eye cover should be checked for gaps and replaced if missing to prevent further ingress of spray.

That makes sense, aren't the Sharan and the Galaxy pretty much the same car?

Correct .

had belt replaced as suggested seems to have solved the problem, thanks very much.