In message , Christian
McArdle writes
My boiler, a Glow-worm space saver F, has stopped working. Its normal
sequence of operation when starting up is that the flue extractor fan
starts running, then a spark electrode lights a pilot light which then
lights the main burner. However, now all that happens when you switch
it on is a clunk and a faint whirring sound (I'm not sure if this is
coming from the boiler itself or just water circulating from the water
pump). There doesn't seem to be any air blowing out from the flue and
there is no sparking at the pilot light. Does anyone here have any idea
what might have gone wrong and how to fix it?

Well, you say the first element in the sequence is the fan starting. There
will be various fail-safe mechanisms that abort the lighting sequence if the
fan fails.

So perhaps the fan is not starting for a reason. Either it is broken, or the
cable to it is, or the PCB is knackered.

There may be other failsafe devices, too. Perhaps the first step is really
to start the water flow and only to proceed when flow is detected. I don't
know enough about the boiler. Hopefully Ed Sirrett or raden will be along
soon with the actual sequence or most likely failure mode for this boiler.

Well, a bit more info would have been useful. It sounds like all that is
happening is that the pump is probably running and the fan isn't. Given
that baseline ...

Diagnostics would require a DVM and carried out in the following order
and can all be performed at or near the pcb

1/ Is there 240V between the live and neutral on the PCB (Blue and brown
flying leads)

2/ Is the overheat stat open circuit as measured at the pcb (yellow and
white flying leads

3/ Are there volts to the Fan ? (connector which plugs into the pcb




--
geoff