i was called to see this worcester boiler which was flashing quickly on hot water which had stopped by the time i got there, the customer had said that she was getting no hot water, the boiler pressure was low so i topped it up to 1.5bar. i looked at the fault codes and put it down to the fan not working properly or air pressure switch but they've had a new fan fitted. i was speaking to the customer today and he said the boiler pressure had gone upto 3.5bar and blown off i was just wondering if anyone else has had this problem , this problem is intermittent could it be a blockage on the heat exchanger aswell