Hello good people - I have a Vaillant Ecotek plus system boiler, controlled by a Honeywell ST9400C. Up until recently everything was working fine with heating and hot water working independently. Then the heating stopped working and only works now when the hot water is switched on. With both on the heating takes a lot longer to warm up and just seems inefficient to be doing both. When i select heating on the Honeywell programmer i get nothing, the pump doesn't even switch on. Yet when i select hot water we have both come on. I am not sure what is going on. I thought it might be an issue with the three-way but then thought the heating shouldn't come on at all if that is the case? Any help much appreciated.