Most likely your gas valve. There are two coils on this valve. Check resistances of these coils they should read no more than about 10 ohms if your getting open circuit on either coil it's faulty.
Mick
July 2008
Checked flow switches, working fine, sent board back for yet another replacement.
Can't think what else it could be
Daniel Owen
June 2008
Just to add to this, tested so far;
Fan (ok)
Pump (ok)
Thermistors (both reading 13Kohm)
APS (ok)
Flow switches (primary a little flaky but opening and closing)
Gonna be testing flow switches independent of water in a bit but it's doing my head in.
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