Ideal Isar HE30 failing to start CH

[garryr999]

Ideal Isar HE30 failing to start CH in the morning until you turn boiler off and on - it then works fine thru the day
Last year it had a new diverter Vv head kit, pcb and heat exchanger after failing to kick in with hot water - anyone got any ideas what is up with it now

 

[diamondgas]

Is the 'c' illuminated when the heating is on? If yes then the issue is boiler related, if no and the display is 'o' then the issue is external controls.