A temperature sensor for a motor vehicle comprises a composite of PTC and NTC thermistors (1, 2, 3) whose overall temperature characteristic (c) is negative with a plateau (P) centered on the normal working temperature (88.degree. C.) to be sensed, so that tolerances in the sensing system and normal fluctuations of the working temperature will tend not to be registered by the vehicle temperature gauge. Thus only abnormal variations in temperature caused by a fault or overload condition will be indicated.