Potterton Netaheat 10-16 MK11 No heating or hot water?

am making some progress... we had a gas fitter replace the gas valve, thermo thing and selinoide thing and we now have hot water ... but no heating!!! We have bled the rads but the boiler just will not fire up when just the heating is selected - only when the hot water is selected??? Is it just an air lock or a blockage??? so near yet still cold!!!

lyn colwyn bay
December 2010

thanks deano for your help but what is and wear is the pcb have draind system and put new pump on filled system back with water bled rads lit boiler but still only pilot light come on has no flair what can i do to get hot water and heating only clicks to light then stops

lyn colwyn bay
November 2010

ignition sequence seems to have stopped at pilot stage. after pilot lights spark should stop firing, control pcb sences this and then powers burner soleniod, gas enters burner and is lit off pilot.
has spark stopped? if not pcb will not open main gas (assuming pilot not lit). (common fault=broken electrode or lead,pilot part blocked not covering electrode when lit & often rectification components on pcb has failed ) if sure spark has stopped check power out to both solenoids on pcb (3 thick wires out bottom left blue neutral. black pilot solenoid. white main solenoid if 240v out on both black & white, gas valve has failed, if only pilot solenoid powered, pcb failed

deano
November 2010