Worcester 28CDi burner lockout

[RobHogan]

A little bit of background (may or may not be relevant) - Just moved in to a new house, the boiler was dead when I arrived with the LEDs indicating an air flow problem, the boiler cutting out after a few seconds of demand. I called out the local gas man and he replaced the fan unit and all was fine for two days.

Now the LEDs are showing a burner lockout (CH demand light is flashing slowly). The fault is there even when there's no demand, and appears almost as soon as the boiler is turned on at the mains or reset.

I've had the cover off to do a bit of amateur diagnostics. There are no sparks from the ignition, no clicking sounds etc at all. I haven't heard or smelt any gas.

I'm thinking it's likely to be a PCB failure. I've read on these forums about sticking gas valves on these boilers, but in all of those cases the ignition was sparking, and presumably the problem only appeared when there was demand. For me it's all the time.

I'd appreciate any thoughts at all from anyone with experience of these things.

Thanks

 

[bengasman]

It could be the pcb, but a bit odd that it would blow 2 days after the fan died.
I'd say this is one of those cases where you have to check the lot and eliminate all else. "Clean" 230V. Fan, aps, loom, corroded/loose connectors, etc etc.
Too often the board is blamed whilst innocent.

 

[Boilerman2]

Hear Hear!

 

[ollski]

Check the air pressure swich isn't sticking in the n o position.

 

[bengasman]

[curtsey emoticon]