On Jun 4, 12:57*pm, chudford wrote:
On Jun 4, 8:58*am, Adrian C wrote:





On 02/06/2011 22:05, geoff wrote:

If you have neither gas or spark, then it would point me in the
direction of the air pressure switch not transferring (for whatever
reason - e.g APS failure, blocked pipes or some other blockage) or hall
effect sensor in the fan, depending on which it has, I can't remember

Thanks Geoff,

Yup, looks like the differential pressure sensor is kaput. Shorted it
out it's connections after the fan came on, and the boiler fired up.
This sensor is mounted near the top of the sealed plenum chamber, and
the tiny vent hole for the switch is clear. We did a suck/blow test of
the switch when we removed it, but human breath is not that well
calibrated I suppose.

Probably have to do some more diagnostics after that to get the DHW
supply working after we've fitted the above. Noted that even though the
microswitch from the diverter valve works (and is switching 30V through
the PCB), it doesn't do a DHW startup. I'll scratch my head on that next.