Nidec Shares Tumble After Scandal Spreads to Product Quality

Nidec Corp. is facing renewed investor backlash after disclosing quality control misconduct involving motors and other products it supplies to other companies, compounding the challenges confronting a once-admired manufacturer on top of accounting problems and the exit of its charismatic founder.

Shares of the world’s largest maker of precision motors fell 14% in Tokyo trading on Wednesday, the steepest decline in six months, after Kyoto-based Nidec said the issues involve changes made to materials, processes and designs without approval. More than 1,000 instances were found in products without customers’ knowledge, with the vast majority used in household appliances.