I have saunier duval 620 . I change diaparam the centralheating working ok but no hot water the pressure . motor . fan everthing ok but no hot water!

roger, March 2007

The facts are not clear.
How much water pressure.
Does the reversing valve turn over to hot water, if not the diaphragm. is at fault it does then it will either be the thermistor ( orange), or the micro-switch.
If the heating is running when the tap is turned on and the burners go out the thermistor is at fault.
One important thing. Was the governor still in the water valve

alan, March 2007