In message , Ed Sirett
writes

When I switch it on, and the fan sarts up, there is a delay, and then
a click of sorts. - I think this is the air pressure switch tripping?
But then - nothing

Th "click of sorts" could be the APS and PCB relay moving. It might also
be the click of the pilot gas valve which would happen 'simultaneously'
with those clicks.

Since there is no sparking the chances are that the spark lead is
shorted

No - you'd still hear the spark gap on the primary discharging, it's
just that it's drowned out by the secondary spark during normal
operation

BTW, did an Indian lady phone you today ?

I took the liberty of giving her your phone number



--
geoff