Sorry I've re-submitted this question because my last question heading was incomplete.
My boiler has been shaky for a while - it's been repaired several times in the last two years (think had the switch replaced and the pump)
For the last few months it hasn't ignited when I've turned the hot water on (the pump works but the gas doesn't flow past the pilot light.) I was able to ignite it manually by depressing and releasing the gas control knob but now that doesn't work. Does anyone have any ideas for what may be afflicting it and how best to repair it - should I contact a repairman?
Many thanks

Turlough, September 2009

more than likely a diaphragm fault, on the excell diaphragm pushes pin out moving a lever arm which makes the microswitch, as diaphragm weakens/holes/splits arm doesn't move as far and starts struggling to reach microswitch, its like a pivot. thats where i would look first off. cheapish part, bit fiddly

x, September 2009

the way this boiler works is; if there is a demand then the pump will run, the flow switch diaphragm will move to make a switch to prove the pump is running, it should then send power to the fan so it runs at full speed, the air pressure switch should then make and send power to the gas valve which should in turn open and allow the main burner to light. at what point is it failing? i.e can you hear the fan running? if so shortly after the fan runs can you hear a small click which is the air pressure switch making?

You'll need to get a qualified engineer to repair it whatever the fault but it's best if you have a rough idea what it is likely to be.

Ian, September 2009

pilot light on and pump is working but will notfire up

gerry hill, September 2009