An arrangement for detecting the interior temp. of a motor vehicle contains a temp. sensor (17) inside a sensor tube (19) which is connected to the vehicle interior (10) to form an air flow over the sensor and to a reduced pressure source in the vehicle. A thermal device (24) which produces an air flow by heating is connected to the sensor tube downstream of the temp. sensor. The thermal device has a stand pipe (21) branching off from the sensor tube, opening into the interior above the sensor tube inlet and coupled to the heat source. ADVANTAGE - Ensures min. ventilation of temp. sensor even when the reduced pressure source fails.