Intermittent Boiler Firing up

[SukhyB]

Need someone’s advice please.
My boiler is behaving very strangely.
The boiler fires up 99% of the time when it is set to start in the programmer. However, when I want it to start manually by me switching it to on, on the programmer, it does not always fire up. It takes me around 10-15 attempts to manually turn on and turn off via the programmer - at which point it will fire up. My first action was to swap the programmer out and the same issue occurred. Note that boiler is fine itself in that no error code appears on the boiler and the manufacturer Confirms it is fine. This leaves me with wondering about the Thermostat in my living room or the Valve in my airing cupboard?!?. I thought these would either work or not work instead of intermittently working. Does anyone have any ideas on this. Any help would be appreciated.

 

[dilalio]

Testing with a multimeter is your best way to fault find on this. Check the switching, throughout the circuit.

 

[Harry Bloomfield]

There is usually a delay in the request for heat and the boiler actually firing. When the request is made, the valve actuator may need to motor to the correct position, then the boiler will probably need to do a purge of the combustion chamber, before finally firing. Are you sure it is not these delays making it seem as if it is not responding?

 

[jeff the gasman]

Things already near demand temperature hold back before firing, multiple attempts to prompt lighting can exacerbate this problem as the anti cycle device kicks in.
Start again with 5 Minutes break at least and see how it goes. Report back.