boiler not firing up after proper ignition sequence is followed, pilot extinguishing itself after ignition button is released. heat sensor which senses pilot flame looks damaged, have cleaned it with emery paper but to no avail. also lots of white powdery build up inside the burner chamber on heat exchangers etc. looks like leak but no sight of water, pressure also drops on pressure guage and needs frequent topping up, any ideas

michelle mcintyre, July 2008

If pilot light is not staying on, then cause COULD be the damaged sensor. This will stop supply of gas to the flame on the pilot light, if there is no flame detected (current to sensor), to stop build up of gas. If no plilot light then the boiler will not ignite.

change sensor would be best bet.

Just a thought as I'm no expert.

richard, September 2008