Hi folks,

My Baxi Solo 2 (non-condensing, automatic ignition) boiler recently
stopped working. The fan runs, there is a quiet repeating clicking
noise, but it does not light.

I investigated myself and observed that the repeated clicking is the
sparking of the pilot light ignition spark gap. The spark is visible,
but the pilot is not lighting. Occasionally it lights just a little
bit then goes out instantly, as if there is a tiny amount of gas
coming through.

At this point, it seemed to me that the fault must either be with the
PCB (not activating the pilot gas valve) or the gas valve itself (not
opening).

The gas valve (Honeywell VR4601T A1046) has a pair of terminals
towards one end, and a group of three terminals at the other end (*).
I guessed from the layout (but it's only a guess) that the pair are
the terminals for the pilot valve solenoid. I found 240V across these
when the boiler was trying to light. From this I concluded that it is
the gas valve, and not the PCB, that is faulty.

To accelerate the repair process and avoid two call-outs, I ordered a
replacement gas valve and arranged for a CORGI-registered engineer to
visit. I hoped he would agree with my diagnosis and would be able to
replace the valve using my part.

Unfortunately I was not in when he called. He bumbled around a bit,
spent some time on the phone to Baxi technical support, and apparently
decided it was the PCB, not the gas valve. I don't have much faith in
his abilities as he apparently said he couldn't see any spark (which
is definitely visible through the observation port) and thought the
clicking was the valve (which I'm fairly sure it isn't). On the other
hand, he is the boiler engineer and he did check various terminals etc
while on the phone to Baxi.

My question: does my amateur diagnosis seem sound? Or should I trust
him? As things stand, I will have to pay for a PCB and two visits if
he is right (I can return the valve I bought), or a PCB, two visits
and a gas valve if I am right. Alternatively, if I was sure enough
that the fault is indeed with the gas valve, I could cut my losses and
get a different engineer out who might agree that it's the gas valve
and just replace that.

Opinions very welcome!

Cheers,

Seb

(*) picture at http://www.heating-parts.co.uk/media/stock/00000555.JPG