Potterton Kingfisher Mf - extinguishing and not re-lighting

[Josephsoap]

My son's elderly Potterton Kingfisher has suddenly developed this problem whereby the main burner flame goes out and doesnt re-ignite. this started happening during the recent gales and we therefore put it down to turbulence arround the balanced flue terminal.
Since the winds have subsided however this still continues to happen.
Once the flame has gone out (the pilot light flame continues to burn). Shut the boiler off and then turn it on and it goes through the lighting sequence and all is fine and then it can be two or three minutes or two or three hours and for no apparent reason the main burner flame goes out. Whilst the boiler has been running we have disconnected the pressure switch tube from the fan and the flame goes out, reconnect it and the boiler fires back up. We have removed the thyristor controling the boiler and the flame goes out, re-insert the thyrister and the boiler fires backk up again. Our thoughts are that it is the gas valve but would welcome a second opinion.
Any thoughts would be much appreciated.
Chris

 

[DP]

Best to get someone who knows how this boiler works

 

[ianmcd]

Whilst the boiler has been running we have disconnected the pressure switch tube from the fan and the flame goes out,

stop doing this, you need someone who is qualified to work on this boiler, you are messing around with safety devices

 

[Madrab]

Without re-visiting the whole DIY gas thing, we aren't allowed to give gas advice on this forum .... as suggested, you really shouldn't be playing around with these things without experience. Problems like this can't be answered remotely without being on site and testing specific components methodically and certainly cant be diagnosed by pulling wires off of the appliances safety devices.

Also as suggested, these old boilers need someone that has experience with them to diagnose.

 

[Josephsoap]

Many thanks to Ian and Rob for their considered advice.
However, I should like to put into perspective the approach to carrying out our own diagnosis of the fault.
The isolation of the pressure switch by removing the plastic tube from the fan housing whilst the boiler was running, caused as expected; the main burner to drop out.
The withdrawal of the thyristor from its housing within the heat exchanger thus exposing it to room temperature after the boiler had shut down after reaching its upper set point, did nothing more than simulate a drop in the boiler's return temperature only quicker.
For Ian and Rob's information and however well intended their advice was meant, I have in excess of fifty years of dealing with "these old boilers", which incidentally by comparison with today's replacements are far more reliable, simple to maintain and were capable of delivering water the right temperature to the radiators/convectors to maximise their effectiveness.
If i should ever be so stupid as to interfere with a mag valve or gas component whilst the burner is fired and further to post the fact on this forum, then I would expect those qualified to advise me accordingly.
To summerise: What has been done in trying to isolate the cause of the problem thus far is no more than anyone (qualified engineer or competent DIYer) would do. What was done was neither hazardous or dangerous.
Lastly, its observations or suggestions as to the possible cause of the problem that would be most welcome, as of course would safety advice were I to having been "messing about" with gas or 240volts AC

 

[danfre]

If you have in excess of fifty years experience working on old boiler's I am surprised you are asking for advice

 

[Josephsoap]

Nobody should be beyond seeking advice danfre, (in my ever so humble opinion of course) "every day's a school day" as they say!

 

[CBW]

What was done was neither hazardous or dangerous.

In what way?

 

[ianmcd]

For Ian and Rob's information and however well intended their advice was meant, I have in excess of fifty years of dealing with "these old boilers",

You have in excess of fifty years of working with a Potterton Kingfisher MF ? now I apologise and I am totally impressed, did you invent them and keep it a secret for the first 30 years ? the first MF went into production in 2001

 

[kidgreen61]

Either way, you are utterly clueless as to how the thing works.

 

[Madrab]

If you have in excess of fifty years experience working on old boiler's I am surprised you are asking for advice

Couldn't have said it better myself.

 

[ianmcd]

Couldn't have said it better myself.

Not gonna mention some of those old paisley boilers you used to take to the dancing Rab

 

[Madrab]

Not gonna mention some of those old paisley boilers you used to take to the dancing Rab

I always thought that was you right behind me in the queue with those old gorbals ones Ian

 

[ianmcd]

I always thought that was you right behind me in the queue with those old gorbals ones Ian

Behind you in the queue with 24" stillies in your bib and brace are you mad

 

[Madrab]

24" stillies

36" in yer dungarees mair like