combi central heating problem

[diyr]

Halstead Ace Combi. Central heating warming up but not getting anywhere near how hot it should be running to.
System has been completely flushed, cleaned and blead. But is no better. Hot water is fine.
Can someone advise, thank you?

 

[Blake]

Hi, could be several things. Have the thermistors been checked to ensure they are reading correctly? If they are faulty they may be telling the boiler it is at the incorrect temp.

Does the flame increase and decrease as you turn the temperature dial on the boiler? Have the burner pressures been checked?