profile boiler repeatedly firing up and going off

[sjd]

Can anyone help please? I have a profile boiler( not combi). It packed up during the very cold winter but a new circuit board saw it back in service. when the plumber left he left the boiler setting on max. I noticed a few days later the overflow from the header tank was weeping. Turning down the boiler setting to 4 seems to have sorted that.
Now the boiler turns on, keeps going nicely for about 5-10 minutes then turns off....then after a few mintues comes on again and keeps repeating the process. it is keeping the house warm but the constant going on and off is driving me mad!

Anyone any ideas please>

 

[Puddle]

The tank was probably over flowing as to full and expansion raising water level to over flow level or thermostat is slightly out of calibration causing slight over heating when on full,however boiler has a over heat thermostat so probable first thought

Boiler coming on and off ,it may of always doing this but you have just noticed as you are aware more of boiler due to problems you have had,however could be gas pressures require adjusting or flow and return temps checked
There also could be another problem with boiler,weak fan,aps or aps tubes,good boiler but getting on now.Maybe get plumber back to service and check over again

imho

 

[Plumbcrazy56]

It does sound like the air pressure switch..They cost around £20 so worth changing before going for the fan option.