On 1 Apr, 21:32, geoff wrote:
In message
,
" writesHi all

I have an Ideal Classic conventional boiler, approx 13 years old. The
CH system is the type having a header tank in the loft. Over the past
few days, it was making a whistling noise and was taking a long time
to fire up (10 to 20 minutes from when it was turned on at the
controller). Today it does not fire up at all, and it makes a fairly
quiet humming noise when the controller is asking for heat. Any ideas?

Is the fan turning ?

Is there a spark clicking away ?

You need to discover at what point in the sequence it's failing

call for heat
if temp sensor considers it's cool and
O/H stat is short circuit
fan comes on
this transfers the air pressure switch
which tells the pcb to
a) spark and
b) open the pilot valve
pcb senses the pilot is alight
pcb opens the main valve

--
geoff

Many thanks for the advice! -it turned out to be the fan in the end

Julian