Ign cycling

[Bamba]

Boiler is Sime Friendly Format (Combi)
Problem is boiler lights then goes out then lights and so on, radiators get nice and warm; water is not as hot as it used to be.
Changed thermocoulple, thermistor, limit sensor, overheat sensor, and frost stat, checked air switch, anyone got any ideas.

 

[ChrisR]

Yep, Find out how the boiler works and stop guessing!
How much £ have you spent!?

 

[kevplumb]

spent that much on a guess

 

[ChrisR]

How long does it stay alight and is it the same on HW as CH?

 

[Bamba]

Yes, it's the same on HW and CH, however I have noticed the fault disappears when lit from cold, once it has warmed up the cycling begins.

 

[Bamba]

Yes, it affects CH and DHW.

 

[DarkInferno]

incorrectly positioned/faulty flame sensor / broken lead

 

[Bamba]

I have now noticed the boiler works perfectly when the time kicks in in the morning that is until I use the hot water then the cycling begins. Could this be a fault with the diverter valve?

Thanks in advance.