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Instead of using the timer, we used the on/off button. This worked until we changed the pump. Now the pump is working, some of the pipes are hot but although all the lights on the controls are on, the radiators are cold and we are not getting hot water. When we turn on the heating the pump starts, but when we turn on the hot water alone, the pump doesn't start. That's why we think its the motorized valve, because when we push the spring on the valve, then the pump will start