My radiators come on when I turn on the hot water

More questions have to be asked - you don't say what boiler make and model or even how old. Mr ali cam - nothing wrong with your boiler

Hello If this is a problem that has always been apparent then it is likely that your boiler and/or central heating system installation is questionable. We would recommend to have both your boiler and piping checked to see whether valves, pipes and links have been laid properly to standard. On the other-hand if this is a new problem we would start by checking the diverter valve and if found that this is the issue we would consider replacing it. If you have recently had it replaced and you still have this problem there could be a number of issues: 1) A faulty new valve 2) Wrongly fitted valve 3) Issues with power to the valve (powered valve) A thorough check and test would establish why the valve isn't working so that appropriate action can be taken to remedy it. We hope this helps

Hello, get the valve checked to see if the heating port is opening when it is on hot water only, it sounds to me like it is wired wrong.