THE HEATER

 To drive safely, you have to be comfortable. Traditionally, most heaters utilise the hot water supply that cools the engine to heat the cabin. The temperature can be varied by adjusting the flow of hot water into the heater matrix, which is, effectively, a mini-radiator mounted behind the facia. Incoming cold air becomes warmed by being directed over the hot surface, prior to being directed through the appropriate air vents. The air-blend principle offers an alternative, where hot water flows unrestricted through the matrix but the desired temperature is made possible by mixing hot and cold air streams controlled by movable flaps within the main heater box.

Modern diesel engines, however, tend not to produce hot water sufficiently quickly following a cold start. While auxiliary diesel-powered heaters are popular in the Arctic temperatures of Nordic nations, for example, you may find that the heating system on Uk-specified cars possesses an auxiliary electric heater that is integral with the heater-box.

Should you work on an electric vehicle, or self-charging hybrid, be wary that some heaters rely on the high-voltage system, meaning that potentially lethal levels of at least 200 volts will be present behind the facia. Should this be the case, take the necessary precautions, including deactivating the high-voltage circuit and buying the appropriate PPE and testing equipment before attempting any repairs.