Central heating is wonderful when it works, but can be a nightmare if it goes wrong. A problem may be due to the failure of one or more of the components - boiler, pump, controls, or immersion heater - or something going on inside the system, particularly the onset of corrosion, which is caused by different metals being in contact through water. Many of the problems that arise with central heating can be dealt with relatively simply, but some may call for the services of a professional contractor.