Abstract: A valve for vehicle liquid heating circuits that includes a sealed case, an inlet, an outlet and a mechanism for opening and closing at least one of said inlet and said outlet. The valve includes a guide means for mounting a member having a rack thereon and rotatable means with a toothed segment engagable with and actuating the rack along the guide means to move a valve plug into and out of engagement with a seat located at either said inlet or said outlet. A rotatable cylindrical element that includes said toothed segment extends through said sealed casing to accept a lever for actuating the segment to thereby move the rack and its associated plug.