My house has a Vaillant Ecotec Pro 28 combi boiler. Our hot taps have just started running cold. The boiler makes all the usual sounds and steam leaves the vent when the hot taps are turned on - but the water coming out is cold. Our heating still works but the one rad in the house without a control seems to be running full tilt, turning that particular room into an oven. Any help would be appreciated.