boiler running 4 heating,but valve wont kick in, to heat hot water.the pin in the valve wont come out to make contact with the switch. possible air lock? or sensor ?
sounds like domestic diaphragm perished, easy to replace. If you make the contact yourself through the micro switch does the boiler ignite? if yes definately diaphragm.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.