Hi I have a vaillant combi-boiler vcw-gb 221 h. still fires up when taps turned on for hot water, but no heat to radiators, can still hear motor running but not firing up for radiators.any info as to fault appreciated.
when you say "motor", is it the circulating pump?
Have you checked if the room thermostat (if fitted) is working properly?
By setting a lower temperature, you should hear it "click".
Try this first, and come back if not OK
2 Main probs on a 221 not allowing heating,are pin on water section not returning completly to rest position thus boiler still thinking it is HW demand . Other is the servo valve worn and not allowing proper water flow through to to pull over the diaphragm and activate the micro switches on the divertor valve . Get someone who knows vailants and will repair without putting unnecesarry parts on.
I have exactly the same problem with this make of combi-boiler.
I called out a central heating 'expert' who has replaced the divertor valve and attempted to clean a bockage to the servo valve. He further recommended flushing out of the system and the addition of an 'additive'. He left with the heating and hw working.
Within a couple of hours the heating has gone off and he is coming back tomorrow to try and solve the problem.
Should I be worried with his diagnosis/think about cancelling his check?