This isnt an answer as such but i hope it can help others. Its longs since in practice i found the answer above to be right...BUT...without much detail so i didnt particularly appreciate some of the more terse things that were said.....my tale of woe....including a fan issue and a pilot issue. Note in advance that if you have issues the FIRST thing you should do is download the user/installers manual of the glowworm site - this was very welcome, is generally an easy read compared to other manuals and has a reasonably idiiot proof trouble shooting guide. To do all this i class my self as a competant person but obviously you need to figure out how competant you are with gas and electrics.
PART 1: THE FAN
1 week ago, to be more precise 1 week of flu ago, the 80ff glowworm fan decided to make its normal 'hey its been 2 years since i last failed' kind of screeching noise. I felt slightly prepared this time, or at least prepared for action since im a bit fed up of shelling out 150 quid to a plumber everytime for a part replacement. I tried various lubricants but no luck. I tried bending the exterioir fan (the metal one below the transformer) but no luck either. From what i read on various forums it seemed to be the bearings. I read about one guy stripping them off and replacing fairly cheaply so followed the instructions and took the main fan unit off with the large screws. I then spent ages trying to dismantle the unit to expose the bear but gave up. I would strongly recommend you dont bother with this rout...far to timeconsuming and difficult. So i found via another post a couple of companies that do replacements.. http://www.cetltd.com/ (very very very helpful guy - see part 2) who do part exchange and also http://www.allsparesdirect.co.uk wo i got the fan from. Around 50£; fitted easy and all was working. Result
PART 2 - PILOT
3 days later it stopped working again, the fan span, the sparker clicked and the pilot came on but the main burner wouldnt. In addition i notted that the plastic external fan which, right at the top of the fan unit, had shed all its blades despite not hitting anything. This turned out to be a red herring i think
I went through the diagnostics and manual micoscopically but probably not micoscopically enough. The thing to know, and which the CET guys advised me in detail of was there can only be a couple of reasons why the main burner doesnt ignite and to be honest by my lack of thoroughness i ended up with a new PCB which wasnt needed. The options are:
1.New PCB - absolutely last but one option
2.New master control unit last option - think better a new bolier here
3.The HT lead is broken
4.The sparker isnt getting a signal
5.the pilot is blocked
6.Signal fault to master control unit solenoid two
I checked point 3; seemed ok. Sparker seemed to be in right position (point 4) in the flame . And the pilot flame was ok (point 5) since when i took of the LOWER pilot to release the tube I could see no issues. Also (point 6) the solenoid continuity seemed fine and it simply wasnt getting a signal from the board. So i went for the new PCB. Cost around £40 fitted easily the next day but the same problem - no main flam.
I read the manual for the 12th time and noted that the pilot flame diagram suggested the flame should be bigger (10-20mm). The pilot length is preset so there are no controls to change this. And from the CET guy he had told me it was important pilot was in the flame since not only does the HT leader feed the sparker...in reverse when the pilot is lit it feeds some other signal back through the flame to the PCB which is detected and this triggers the main jet solenoid. As i was messing around the area to get the sparker closer to the flame (which proved impossible) the HT lead fell from the igniter ceramic so i assumed this was a hidden fault and got an igniter (£15) from local plumb shop. I mounted it but same problem. So i came back to the size of the pilot. Days before some workmen are putting in a new front garden for me and managed to sever the gas main so i wondered if either the repair from the gasboard wasnt right or the concrete later poored over the pipe repair had somehow compressed it. So i called out transco (very helpd ful guy) who confirmed pressure was ok, look at my boiler as well (turning a blind eye to the sheel it was by now) but still no luck. He did talk about dust in the system though. Finally i looked at the based of the pilot again for dust and took the nut holding the pipe of and this time and additional nut which goes into the pilot housing AND importantly, but not obviously, contains some kind of perferated seramic with two hair-like perferations in it. I cleaned them with a small wire and blew like hell (they didnt seem blocked though). Reassembled and since then works like an old dream again.
So if i live my life again or you do and your main burner isnt ligting yet the pilot is lit AND the sparker just continues to spark then....
Look to see if the pilot flam is around 10-20mm and imerses the sparker and probably the sparker should glows a little. If it doesnt then to be sure try using a lighter on the sparker and see if it ignites. If it does then probably your pilot has dust in it so take all the nuts of until you find the nut with the two holed ceramic and clean it
If the flame is the right size then check the HT wire. It might have enough continuity to carry the HT spark (since it jumps across breaks) but NOT the signal in reverse. Pull and push it from the sparker, the board and along its lenght. if you suspect anything replace it its only15£ and probably if i bought from CET it would have been cheaper
If you get to here and no luck then put a multimeter across the PCB solenoid output and check then black/brown wires. One is for the pilot solenoid and the other for the main solenoid. If the main solenoid signal raises then its the master control unit (hardware) and if it doesnt then its the PCB
Anyway hope this can help others
Stuart Campbell
October 2010
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