The problem was due the insulation board in the combustion chamber breaking and consequently covering the pilot assembly and burner.
It was a blessing that the problem did occur so I was able to fix it.
To correct the problem I simply put back the insulation material using the metal clips. To be safe I will replace the insulation board that broke. Can these be bought?
Actually I will elaborate on my experience which may come in useful to anyone out there...
My system has had a problematic PCB board for some time. The symptom being that the ignition sequnce would not start and the only way to get the heater to light was to sightly pull on the circuit board. This clearly indicated a PCB dry joint or loose connection somewhere.
In the meantime the pump broke (which may have been a consequence of the problematic PCB board, I don't know).
I called an heating engineer out and since the system was out of service I took off the PCB. SOme of the connections on the PCB were really tight and needed some force to pull off and put back on. There was a joint which was loose and moving. So after re-soldering the joint I refitted the PCB.
Anyway the plumber came and fixed the pump (nice informative chap). While he was round I asked him to service the boiler and he did the pressure, flue checks and cleaned the boiler etc.
After he left I noticed that pressure of the system was decreasing quickly which indicated a leak in the system somewhere. Water was coming out of the discharge pipe outside, so the problem seemed to be the pressure release valve (note this is a red spring valve- is this the right term?). Now I believe the plumber drained the system using this valve (which probaby is not the best thing to do) and as a consequence, the valve started letting water through. After looking in the forum here it appeared that the valve did not close properly (probably some particle stuck) and after phoning the plumber, he suggested opening the valve a few times to free any particles there. I opened the valve slightly and water came out. I fılled the system and checked the pressure but the pressure kept falling. I did this twice without success. I then fully rotated the valve till it sprung back. I did this a couple of times and refilled the system. There is no leak coming from the discharge pipe and the system pressure is now stable. So the valve was the problem.
Anyway the saga continues... Just as I thought I would have a relaxing weekend, the PCB started playing up again. This time not as before but oddly not relighting unless the cables were moved slightly but clicking differently. Again a funny connection somewhere. So I decided that I would have to check the PCB again. It seems that removing and refitting the pcb the first time caused some further damage to the board or maybe I didn't fix it the first time. ANyway, before I did this, the problem that I described at the beginning of the post occured so I thought, shoot the pcb is really bust. So I soldered quite a few dry joints and refitted it. Many of the dry joints were where plugs connect to the pcb... This made no difference. So I thought I better ask the forum...
So many thanks for your advice.
Hope my story comes in handy to someone. I am sure I will be back with more questions and experiences
