To perform a factory reset on the HAKKO FR-872
IR Preheater, press and hold all three buttons on the face of the FR-872 simultaneously while turning the preheater on.
When this is completed successfully, the display on the right will show the firmware version of the unit, and the display on the left will show a value of 'y' indicating that the unit is waiting for a confirmation to execute the factory reset. Use the dial control to select a value of 'n' if you do not wish to proceed with the factory reset. Once you have made your selection, press the asterisk (*) button to accept the value and the factory reset is complete.