vcw 242

Hi yes I know this is an old combi boiler. I've had it for 22 years and it was in the house at least 5 years before we move in I believe. Boiler fire up fine. CH is fine. DHW activates diaphragm->servo->diverter valve, boiler starts and the heat exchanger gets hot. Water from tap gets hotish...

Hi I have a Vaillant vcw 242 eh, the hot water is working well on it and is getting up to a good temperature to flow rate. The problem i am having is with the central heating. When the thermostat is clicked on it fires up, but if you click it down and then click it back on again the boiler...