Any Glow-worm boiler experts out there? Geoff, maybe?

[Roger Mills]

I'm at my holiday property at the moment, and the boiler has just gone on the blink!

It's a 10-year-old Glow-worm Ultimate 30FF, and has worked perfectly until now. The symptoms are as follows:

• The first neon indicator is on, but none of the others are

• The fan runs for about a second, then there's a click from a relay in the control box, and it goes off for a couple of seconds. Then the whole thing repeats with an (approx) 3 second cycle time

I have an installation manual with a diagnostic chart, but the boiler is high up in a cupboard with poor accessibility (no, I didn't install it!) so it's difficult to do all the voltage checks it suggests. There is one point in the chart where it asks whether the fan is 'hunting' and, if yes, suggests changing the PCB. So that may be the solution - but is there anything else obvious to look for?

TIA.

[Cicero]

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You could start by cleaning out the tubes between fan and pressure switch. Also check that the metal tubes /holes (to which the tubes are attached) on the fan housing are clear of dust and debris.

Cic.

[Andrew Gabriel]

My thoughts too. After starting the fan, it's going to be checking for air pressure difference (assuming it has such a check), although seeing a pressure difference after only 1 second sounds a little optimistic. Is the fan fully run up by then?

[geoff]

In message , Roger Mills writes

The critical question is whether the air pressure switch is working or not, the timescales are borderline between pcb and APS

Forget about cleaning out the tubes, the pcb (202142 or 202200) will continue to supply the fan ad nauseum until the APS transfers. If the APS microswitch transfers but the contact resistance is high, the fan will not have power.

The easiest way to test the APS if you only have a bucket and spade but no multimeter, which I wouldn't recommend you to do of course, would be to remove one of the tubes to the APS at the other end and suck or blow to see if that brings on the spark. Like I said you shouldn't do this and really shouldn't do it for longer than necessary to check the APS out

If the APS is OK, then the next thing to suspect has to be the pcb (assuming that you've checked for broken wires in the loom etc)

[Roger Mills]

Thanks to all who replied. The diagnostics seemed to be indicating the PCB, although I wasn't totally convinced. Anyway, since I was leaving the next day, I couldn't frig about for too long so I got the bloke who used to service it for the previous owner of the property to have a look. He was convinced it was the PCB, and came back the next morning with a new one which he fitted and it seems[1] to be working. The cost was quite a lot more than Geoff's recon units - plus labour - but I've kept the old one in case I need a recon one in future.

[1] The boiler is certainly firing and heating the HW and radiators but I wasn't there long enough to check that things like pump over-run are working correctly. I notice from Geoff's site that there appear to be two different PCBs for this boiler depending on whether or not pump over-run is required. The layout of the new board was not quite the same as the old one in terms of things like fuses being side by side rather that at right angles, and the same thing with connectors - so I *hope* it's the right board!

[geoff]

IF it has two fuses (and 7 flying leads) it is the version with pump overrun

There was, for a time, a blue board with two fuses side by side and LEDs, but I haven't seen that version for a long time