when my heating is on and i switch to hot water as well the boiler stops i have changed the pcb but now i think it could be the 3 way valve has anyone any ideas
sounds like an air lock in the system when the hot water circuit is included in the circulation. Check that you have air vents on both sides of your pump - one for CH and one for HW. These release trapped air from the very top of the system causing potential air locks to escape. The smallest of air locks will prevent the pump circulating and the boiler will lock out due to overtemp
tim
November 2009
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.