A portable heater incorporates a housing, heating element, outlet for heat generated by the heating element, and diagnostic testing capabilities that test for defective or abnormal conditions of various safety features and report their status. The features include an object sensing or cover detect function, which operates to disconnect the heater from the primary power source in the event an object is detected that may obstruct the heater outlet, a tilt sensor, which detects whether the heater has been tilted, a fuse, and a positive temperature coefficient (PTC) breaker. The diagnostic testing function preferably receives power directly from the primary source of power to enable the status of the tests to be displayed whenever the heater is plugged in. Light emitting diodes preferably provide backlighting to icons representing the various features to indicate their status to the user.