geoff wrote:
In message , Jeff Layman
writes
Paul wrote:
our 4 year old boiler has started to intermittently give a no flame
detection fault code. resetting the boiler usually cures it for a
day or two. is this a common problem on these, and is it an easy
fix.

We had a Worcester Bosch 3-year boiler exhibit a similar fault,
except that after it was off for a while, it would work for an hour
at most. The PCB was changed, the FFD was changed, and the fan pressure
sensor was changed without improvement, although after these were
done the boiler worked long enough for the CH engineer to go to
another job each time. The CH guy eventually found by sheer luck
that there was a tiny split in the rubber hose from the fan unit to
the pressure sensor. Of course, it was on the back of the hose, not
visible from the front. Cutting 5 mm off the hose solved the fault
and the boiler has worked perfectly since. It seems that the split did
not affect the working of a cold boiler,
but once it had got up to temperature the split opened enough for
the pressure sensor to assume that the fan wasn't working correctly.

But a split in a tube to the APS has nothing to do whatsoever with
flame sensing

Not a similar fault at all

Perhaps I should have chosen my wording more carefully. Sometimes when a
fault code appears, it may lead you in the wrong direction.

In my case, the WB showed a flashing lockout light. According to the
fault-point diagram it was Fault E, and if the fault was not a gas supply
problem, it could be rectified by replacing the spark electrode or HT leads,
replacing the PCB, replacing the gas valve or cable, or replacing the flame
sensor or cable. As previously stated, it was none of these. It should have
shown as Fault B, with only the demand light on - that would have included
replacing the APS tube.



--
Jeff