Tough, it may be the electronic control panel that sits behind the heater controls, if it is, the replacement including labour will cost you several hundred pounds. The first thing to do is to to test the valve that you get to from the engine bay which can be done by removing the wire conection and testing it to see if it shunts open and closed. If it does the valve will not need replacing (if it doesn't you will need to buy a new one from eBay - about £14.00), if not, you are in trouble.
Mike Clement, May 2008
