HENRYS AND SOME OTHER NUMATIC VACUUM CLEANERS DO HAVE TRIP SWITCHES. THEY ARE LISTED IN THEIR SPARES CATALOGUES AS "OVER TEMPERATURE TRIPS" AND ARE BETWEEN THE SWITCH AND MOTOR, IN THE CIRCUIT, ON THE LIVE SIDE. THEY ARE PHYSICALLY LOCATED AGAINST THE MOTOR BODY SO AS TO BE SENSITIVE TO EXCESS HEAT. IF THIS HAS FAILED OPEN CIRCUIT THE MOTOR WOULD NOT RUN. IT DOES NOT APPEAR TO BE SOMETHING YOU CAN RESET.
GEORGE FAWCETT, November 2007