Mitsubishi Electric faked train AC inspections for 35 years, with a data program

In June 2021 Japan's railways learned that the air-conditioners cooling their trains had never been tested the way customers paid for. Mitsubishi Electric's Nagasaki Works, supplier of train air-conditioners to JR and private railways across the country, had since about 1985 either run tests under easier conditions than agreed, skipped them entirely, or typed fictitious results into inspection certificates. JR East alone had roughly 9,800 of the units in service; door-control and brake-related products were later added to the list.

This was not a junior clerk cutting corners. The works had used a dedicated computer program, in place since around 1985, that generated natural-looking data for tests never performed, and falsified compressor inspections continued from 2006. Management also handled disclosure badly: the company knew on 14 June 2021, told regulators and customers from 25 June, stayed silent at its 29 June shareholders meeting, and only confirmed the story after newspapers broke it. President Sugiyama Takeshi conceded it was organised misconduct and resigned in November 2021.

The cracks widened on every inspection of the inspection. ISO 9001 certification of the Nagoya Works was suspended on 5 November 2021 over separate improper conduct at its Kani plant. The external committee's final report on 20 October 2022 counted 197 confirmed misconduct cases — 112 judged intentional, 54 with active management involvement — after finding 70 new cases at 11 additional plants, and Mitsubishi Electric added ten more current and former executives to its disciplinary list, including a former vice-chairman once thought uninvolved.

197 confirmed misconduct cases; new fraud at 11 more plants in the final count; president resigned Nov 2021; ISO 9001 suspended; JR East alone ran ~9,800 units

Delivery schedules and test costs made falsification routine; the program turned a lapse into an institution that survived four decades and several management generations.

Customers trusted the certificate, not the process — no railway re-tested units it had already accepted.

Internal reporting rewarded clean results, so the fraud propagated rather than surfaced.

Disclosure was managed as public relations: weeks passed between internal knowledge and public admission.

A test that always passes is not a test. When inspectors own both the measurement and the record, verification dies — a bespoke program that invents realistic data means the factory already knows.

The external committee chaired by a former Supreme Court justice issued its final report on 20 October 2022: 197 cases of misconduct, just over half intentional, management actively involved in 54. Ten more serving and former executives were added to the punishment roster, and the case became shorthand in Japan for quality-governance failure alongside Kobe Steel and KYB. Mitsubishi Electric has since rebuilt its inspection and compliance framework under the reform plan the committee demanded, and no accident was ever attributed to the falsified units.