i have a potterton performa 24the temperature control knob when turned up or down doesnt have any effect the boiler keeps going even if i turn it down any ideas

eric, January 2013

check the heating micro switch is deactivating on the diverter valve. there should be a pin that come forward to turn the micro switch on then retracts when heating should be off . if it retracts then maybe a new micro switch if it doesnt retract most likelt the diverter valve is clogged up with dirt. strip it and clean it

kash, January 2013