Authorities say Haidl died at Hoag Hospital in Newport Beach of natural causes.
Haidl was a wealthy businessman who earned most of his money from his Nationwide Auction Systems, which he later sold, along with real estate and other interests. He gave former O.C. Sheriff Mike Carona hundreds of thousands of dollars in cash and gifts and in return was appointed assistant sheriff, though he lacked any real law enforcement experience.
In 2007, Haidl wore a wire to help collect evidence against Carona in a witness tampering case. Carona was convicted and sentenced to five and a half years in prison, which he began serving in January 2011.
Haidl later pleaded guilty to tax evasion and was sentencing to probation and community service.
In a statement to the Orange County Register, Haidl's family said, "He died as he lived, surrounded by the people he loved. He will be greatly missed by all who were privileged to know him."
Funeral services are pending.
City News Service contributed to this report.