On 22 Jan 2007 10:17:56 -0800, "cynic" wrote:


T i m wrote:
Hi All,

Some good friends asked me if I knew any good heating engineers and
pre passing any names on thought I'd have a quick look at it myself (I
had helped them change the blower in it a few months ago).

It goes like this ..

Power on, fan spins (good blast of air outside) .. 30 sec later gas
control solenoid pulls in (presumably 'pilot stage?) and electronic
igniter tries to fire up the pilot. After a few tries (it's always
been like that apparently) the pilot lights but immediately (.75 sec)
goes out with a loud sort double clunk from the main gas valve and the
cycle repeats.

I've checked all the obvious (air pressure / flow? valve switching
over, wire all intact, pipe all in place etc) and am about to get /
fit a new HT lead as I thought I heard it arching out somewhere and
also though it was part of the flame failure detection cct (and
hopefully it's cheap) but I don't feel confident it is that?

Failing that (ouch) then could it be the electronic igniter / pilot
control box doodad (407676 / £100, I've checked the back of that for
dry joints and it looks ok) or what else please?


Check the ignition lead forms a low resistance dc path from electrode
to control box. A break will jump the spark but not register the flame
presence

Hmmm, I've just replaced the ht lead and sparker probe (£10 minimum
order at the local place) but no difference (but cheap things to swap
out at the beginning)?

I didn't measure the probs resistance to earth (but still can) but
guess if a new lead didn't fix it then it's back to the control unit?

'If' the spare control unit my mate has unearthed works I might be
tempted to pop the top off the old one and see if there is anything
obvious that could be replaced?

All the best ..

T i m