Importance

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Abstract

A vehicle heater, which contains a heating circuit, connected to an engine coolant circuit, with an auxiliary heating apparatus that is operable independent of the engine and a vehicle heat exchanger installed downstream from the heating apparatus. This heat exchanger, for example, radiates heat to the vehicle interior. With such a vehicle heater, in addition to a built-in temperature sensor, which detects the temperature of a heat exchange medium in the heating apparatus, another temperature sensor is provided, which detects the temperature in the output area of the vehicle heat exchanger. The temperature values detected with the two temperature sensors are then compared and a temperature difference value determined, which serves as characteristic magnitude for indicating the existance a heat requirement. If this temperature difference exceeds below a predetermined temperature difference value, a heat requirement exists in the heating circuit of the vehicle heater and the auxiliary heating apparatus is turned on. If, however, this predetermined temperature difference value is not reached or exceeded, the heating apparatus itself remains turned off, even though the turn-on temperature, on the basis of the temperature sensor provided in the heating apparatus, is reached, since, by comparison of the measured values of the two temperature sensors, it can be detected that no heat requirement exists in the heating circuit.

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First Claim