Potterton Netaheat 16/22 Mk2F 905371 Gas Valve

[MERR]

My cousin has a Potterton Netaheat 16/22 Mk2F the fan on which turns on then the pilot light comes on but the main gas doesn't come on. He thinks the 905371 gas valve may need replacing. But has tried one from a spare gas boiler he has and that didn't work. Can anyone comment on whether they think it could be anything other than the 905371 gas valve required? Also does anyone have a 905371 which are no longer available via internet parts suppliers? Thank you for any comments you make. Mel Robinson

 

[waterworks]

Hi the Mk2F gas valve is still available it's the Electronic model which is now unobtainable although that is a slightly newer model.

On the end of the Mk2F gas valve is a mercury vapour switch which could be your problem it unplugs from the gas valve and is sold seperately.

 

[tonybhoy]

I've most of the parts for this boiler ,all second hand, Gv ,MVS,PCB,Fan,ignition board etc etc.

PM if interested.

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[MERR]

Dear Gentlemen,

Thank you for your comments and parts info. I ordered a 905371 gas valve yesterday from an internet supplier. It can be returned if it doesn't fix the problem. My cousin says he has already tried replacing the mercury switch. So problem remains a mystery. As I said before, I think it is unlikely his spare gas valve would also be faulty. I will let you know the outcome when I have further info.

 

[MERR]

Hi,

As more or less predicted, the replacement gas valve didn't solve my cousin's boiler not starting problem. Apparently the pilot light didn't even come on with the new valve......which it had been doing with the allegedly faulty existing valve(s)..... my cousin isn't CORGI Registered he's DINKY Registered..........but is unlikely to blow himself up or poison himself by pumping CO into the house............circa £200 gas valve will have to go back......not currently obvious what problem is........my cousin did try a new mercury switch previously and that didn't fix problem.........as far as I am aware what is meant to happen is various things like fan then pilot light switch on before main gas valve is "allowed" to open.....so I think the problem is with one of those other things but not sure which........with existing gas valve the fan and pilot light both come on so doesn't look like "problem" is with those items........

Will welcome any additional suggestions and otherwise will let you know when or if problem is solved

Merry Christmas and Happy New Year

Mel

 

[Agile]

Its very expensive blindly changing parts rather than properly diagnosing the fault !

The most obvious cause if no diagnostic checks have been done is that the mercury switch is not reccognising the pilot flame.

I seem to recall that there is a series resistor built into the end of the gas valve assembly and that can fail.

However, I do not give advice on gas related matters to non CORGI registered people and the only suggestion I would have is to get a competent CORGI who can actually diagnose the fault.

Tony

 

[MERR]

Dear Tony,

Thanks for your comment re series resistor possibly failing. My cousin will be able to check whether that is separate from any item he has already tried changing. He doesn't operate entirely by trial and error but probably isn't quite as systematic as I would be if I was attempting to solve the problem............which I may yet do.......In the past my cousin has said he reckons CORGI fitters also use the try it and see technique.......but to what extent he is correct in that view I wouldn't know.

With regards

Mel

 

[Agile]

There are unfortunately many CORGI registered people who have no diagnostic skills and either dont attempt to repair boilers or do a combination of bothering the manufacturer's tech help and guessing what might be at fault.

That would not matter as long as they didn't charge the customer for the parts used.

Tony