Abstract: A thermally responsive electrical switch has a contact arrangement mounted within an open-ended chamber in an electrically insulating switch body, the body having a rim around the open chamber end and having a shoulder formed in the rim which also extends around the open chamber end. A thermally conducting cap is secured over the open end of the chamber engaging the rim of the chamber and a snap-acting thermally responsive bimetal disc has its periphery disposed between the cap and the noted shoulder for positioning the disc relative to the contact arrangement. A motion transfer pin is movable in response to snap-acting movement of the thermally-responsive disc to move the contact arrangement between open and closed circuit positions during temperature changes.