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

--
geoff