We have moved in to our new house only 3 weeks ago. When we turn the heating on the upstairs radiators were working fine but the downstairs radiators were ice cold. We have tried bleeding it and draning the system. If we turn the radiators off upstairs than we do have heating downstairs. But if we turn the radiators upstairs on again then after a few minutes the downstairs radiators are getting cold again. We had 2 servicemen here from 2 different companies. The only thing they have done was tearing up the floorboards and the second one have changed the flow switch .. but still no luck. The boiler was replaced 4 years ago, so it is relatively new. The plumber said that the pump is working. The property was empty for quite a while before we have moved in. But it is 3 weeks since we have moved in and still no heating and it is snowing again .. it is really cold in the house. Either we have hot radiators upstairs or downstairs. Many thanks!