baxi solo 15he ignition lockout

[phil hair]

hi, been to a baxi solo 15 he with ignition lockout fault.
seems to run though the ignition cycle, can hear the gas valve open but not sparke.
It fired briefly when i disconnected the earth from condensate, but went out immediately.
condensates dry, changed the sparker because of continuity problems on the wire.
dont want to shell out on a pcb, any ideas what it is?
earth problem?

 

[Aquarius]

Electrodes been checked?

 

[phil hair]

yes, replaced them as dodgy continuity, pulled the wire out of one of them, but not the problem

 

[Aquarius]

Have you checked polarity? Could be rectification fault.

 

[ShaunCorbs]

Flow switch link it out to test

 

[phil hair]

Flow switch link it out to test

would the fan work if the flow switch not working?
it opens the gas valve but no spark, like when the condensate is wet,but its not.

 

[Allgoode]

Condensate syphon?, seen that before either blocking/restricted draining causing flame lift or the x2 wires on top of syphon trap.

 

[phil hair]

It was the board, of course it was the expensive item.......
I didn;t want to take the plunge without checking there wasn't a trick i'd missed.
thanks everybody