Halstead LPG combi boiler firing up intermittently

[Ramptonwreck]

Sometimes the boiler does fire up sometimes it doesn't. This is the case for hot water and central heating.
I basically switch the boiler power on and off to reset the start up sequence until it lights. The sequence is that the gas valve (I believe) makes a single clicking noise and then the ignition electrodes either produce a series of clicks, ie sparks. Or they don't. If they do produce the sparks it lights and works fine, if they don't produce the sparks the boiler doesn't light. Each start up sequence seems to have 3 attempts before the system locks. Then I power off and on again.
I've checked the voltage to the gas valve which is 220V whether the boiler lights or not.
Halstead think its either the gas valve or PCB but either cost about £150 so I need to be pretty sure before I purchase them.
If anyone can shed any light(!) on this I'd be very grateful
Thanks

 

[spacethegas]

you need an rgi

 

[Ramptonwreck]

Thank you for your reply but I don't know what you mean by a rgi? Please can you explain
Thanks

 

[spacethegas]

Sorry "rgi" means Registered Gas Installer.

its not a diy job.

 

[Ramptonwreck]

You say its not a job for a diyer but unless you use the Halstead boiler engineer then no-one carries Halstead spares, and as far as I've seen these days rgis just swap components in and out until they fix the problem. I'm wondering if anyone knows from first principles what the problem is. I'm an engineer myself and don't really want to pay a few hundred pounds fixing a boiler using the component swapping method if I can either fix it myself by replacing a thermister or something basic or actually just replace the boiler with a newer model.
Thank you

 

[spacethegas]

a good rgi who knows how to boiler fault find will locate the correct fault & replace any parts as necessary. parts are readily available, most can be obtained the same day or if not within 24 hrs. what gives you the impression that we don't carry various manufacturers parts & that parts are just changed willy nilly.
its still the case that if the fault was diagnosed as the gas valve for example it would have to be fitted by a competent person (rgi).
also an rgi is best positioned to advise as to whether you should consider boiler replacement.