vokera lineamax floor standing combi

[brians001]

About six year old boiler, CH problem- runs up to temperature nicely, but when at temp gas valve does not modulate, continually shuts down and restarts on boiler stat.
Gas valve modulates on HW
New main pcb fitted
new thermo couple fitted
all still same
any ideas???

 

[nickso]

New main pcb fitted
new thermo couple fitted

thermistor you mean?

 

[Ray84]

i think youd need to get someone confident on the lineas for a second opinion as theres not much else to look at.
How do u know the minimums been set on the gas valve? do you know what the figure is?
the fact that the heat comes through ok to start proves its not a diverter valve/hw flow switch fault
so id still say faults with the thermistor.....double check it is the heating thermisitor thats been replaced and not the water side one??

please let us know how you get on

Ray