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Worcester Bosch 240RSF burner not firing up

Postby Naegood » Tue Nov 10, 2009 8:46 pm

Worcester Bosch 240RSF combi boiler.
Soft water, high mains pressure.

Here's the problem:
I had replaced the pump head a couple of weeks ago as the old one's bearings were worn.
Simple enough job:bled radiators, vented pump. Heating & hot water from the kitchen taps operating nicely. The cold pressure was about 1 bar and when operating was around 2 bar with no fluctuations.
All OK for a couple of days.
Then when running a bath, the water was initially hot and then cut out. Tried with all the rads off, but no change. Now the heating wouldn't operate either.
Remembered a previous fault when I replaced the diverter valve, so I cleaned out the valve, and replaced the diaphragm which was rotten and worn through.
Filled the system, bled rads, etc, all water tight. Diverter Valve operates when hot tap turned on, but - still no heat or hot water.
Pilot light is on, but burner doesn't fire up when demand is created.
I've tested the pump electrically and it's working.
I've also noticed that the green 'demand' light on the front panel does not light up regardless heating or hot water demand.
The problem I would guess is electrical, but how do I decide where the fault is? Operating switch appears OK, can't see any loose connections.
Can anyone advise, please? :?
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Simply Build It

Postby htg engineer » Wed Nov 11, 2009 8:24 pm

My guess would be PCB - check it, 240V to PCB ? nothing happening > change PCB.

htg engineer
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Postby Naegood » Wed Nov 11, 2009 8:45 pm

Thanks for the suggestion, I'll see if I can figure that out.

Forgot to mention the orange 'power' light is on but seems to flicker, and although the pilot flame remains lit, I am sure I can see sparking in it.

If the PCB's gone I might just throw the towel in and dip into the nest egg for a new boiler.
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