To make a new control unit succeed the operating condition of an existing control unit even when the versions of the control units before and after replacement are different.

This method includes: an operating condition data readout step in which a control part 31b of a new control unit 20b reads out first version status data 42 held in an E2PROM 40a of an existing control unit 20a when a switch 21 of the new control unit 20b of a second version is operated; a version determining step in which a control part 30b of the new control unit 20b determines whether or not the version of the new control unit 20b is different from that of the existing control unit 20a; and an operating condition data writing step in which the control part 31b of the new control unit 20b converts the first version status data 42 into second version status data and writes it in an E2PROM 40b when the version of the existing control unit 20a is different from that of the new control unit 20b.