The instructions say the pilot is pre set and no adjustment is required. I will check further when I can find the time but it is not a job I want to start late in the day and at present I am trying to rebuild a fallen boundary wall before the rain returns so am outside for much of the day.
Something was marginal. The activity that prompted me to raise the problem here was a long sequence of short term firing with nowhere near enough heat output to get the house up to temperature. However since then there has been only the occasional failure which has made tracking down what is going wrong all the harder.
Probably later rather than earlier. I want to have a look at the pilot light and I am still trying to see whether the gas valve loses volts at the same time as the burner goes out but the boiler is now on its almost best behaviour and I have just one odd occasion where the volts appeared to drop for upwards of half a second without affecting the main burner but was that just a probe losing contact.
The lead is relatively new. (Well only 5 years old).
I am fairly sure I tried Plumb Center before trying HRPC the only time I needed one.
I was driven in by the rain this pm so have had a look at the pilot flame. From the inspection window the flame does seen to be enveloping the electrode but after taking the front off the boiler I found that the guide wasn't pointing quite straight at the electrode so I twisted that straight rather than attempting to dismantle the assembly and clean the pilot jet.
On firing up the boiler again it was playing silly buggers for a time so I put my meter across the main gas valve and watched. No drop in volts while the main burner was firing so the drop reported above probably was a probe losing contact. However ISTM that the main burner might be going out before the volts drop rather than after which I think points to a gas valve fault rather than an ignition fault but by the time I came to that conclusion the boiler had reverted to normal operation and I couldn't do another check.
What I have noticed is that when the pilot light stays lit there are still one or two sparks before the main boiler fires which (if I understand correctly) points in the direction a a flame sense fault.
Needless to say I am now more confused than ever.
Going to rain again on Thursday so I will attempt to dismantle the pilot light assembly then to see if it does need cleaning. Hopefully I can do this without damaging the ignition lead.
One of my problems is that I only get a brief glimpse of the pilot flame before the main burner fires up. Is there any way to persuade the pilot to light without the main burner firing almost immediately? I tried disconnecting the lead to the main gas valve but that cut the ignition for some reason. Too clever by half these modern boilers. :-)
That's because the moulded 3-way connector does the pilot as well as the main valve. You can pull the main valve connector out of the Molex (pushing the locking barb down to do so) to get just pilot running.
The message from John Stumbles contains these words:
Thanks John but I can't see why that would be be different from pulling the connector off the terminal at the other end of the white wire.
I had the pilot assembly to bits and gave it a clean it didn't really need and the end result is the same as before - no change. Boiler misbehaves for longer than I am prepared to watch it for before reverting to normal, or almost normal working.
So I am now in the position that so many repair men find themselves in constantly. :-) About to replace components one by one until the problem is solved. On the assumption that the control module is going to be cheaper than a gas valve and more easily sourced Geoff can expect a telephone call some time tomorrow (Thursday).
Any pointers for a gas valve supplier. (Honeywell VR4700E1034. Potterton G.C. part numbers 907704 and 395796).
The boiler was firing this am when I got up although the house was not up to temperature so I turned the supply off and removed the white wire from the main gas valve before restoring the supply. The start-up sequence didn't so I left it on just in case the turn-off had triggered the over-run phase.
After some minutes the start-up did commence but not to the extent of ignition of the pilot light so I touched the detached wire to its terminal and the boiler fired up. Removing the wire again left the pilot flame alight (at long last!) and FWIW the flame looked perfectly healthy to me.
Got some further advice from John at Cetltd this am (for which much thanks) which further muddies the waters. Fault could be with the pressure switch.
John's detailed advice was to check the resistance of both the NC and NO connections on the micro-switch and to check for air leakage. The resistance on the NC circuit was OK but I was unable to persuade the pressure switch to switch by blowing in either tube (I didn't want to blow too hard having been warned about possible damage) so couldn't complete the tests.
As I see it the pressure switch is the most likely candidate (not withstanding my failure to check it out properly) as the boiler problem certainly seems worse when there is a gale blowing outside so I intend to replace that first.
Pressure swithes don't appear to be on Cetltds supply list.
A quick google throws up keeptheheaton.com as a supplier. Before I commit to them has anybody got any experience dealing with them?
It should click over with a very gentle blow - sort of as much as you'd give to make a candle flame flicker but nowhere near as much as to make it go out.
The message from John Stumbles contains these words:
Does it matter which tube?
Because the ends of the tubes close to the pressure switch was so ackward to get to I was using the remote ends. Perhaps they are just too remote for the switch to notice a shortish blow.
Pressure switch now on order and should be delivered Monday.
If that doesn't do the trick it will have to be the pcb and after that the gas valve. I wonder at what point I should start thinking about a new boiler.
I may have got the wrong end of the stick but I am under the impression that the switch needs the normally closed contacts in the initial sequence and that just shorting out the normally open contacts was not an option. I don't have either the equipment or the ability to wire an over ride switch in parallel to the NO contacts and in any case the die is cast so unless the boiler completely ceases to work I don't intend to try anything else untill the new switch is delivered.
The online suppliers are all OK. Part Centre (HRPC IIRC) are part of the Wolseley group and have taken up an anti-diy policy, how they police this on line? I expect they don't.
The pcb tests that the APS is in the NC position initially to prevent a false signal in the event that the APS contacts had stuck (welded themselves) in the normally open position
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