The invention relates to a device of the valve type comprising a housing having a fluid access (7) which is shut off by a shutter (9) secured to an actuator (10) as a function of the temperature of the fluid passing through the device. In order to improve its operational dependability, and reduce its cost, the device comprises an expanding-material back-up thermostatic element (22) lying in the stream of fluid passing through the housing, to actuate the shutter (9) when, as a result of defective operation of the actuator (10) or of its control gear, the shutter has not been moved by the actuator, which also consists of an expanding-material thermostatic element containing heating means (13) connected to its control gear.