Abstract: A heating, air conditioning, and ventilation mechanic was working on a York heating and air conditioning unit (Model No. SS092-E040-46A; Serial No. HM-277435). On June 23, 1995, the employee had responded to a service call reporting a lack of cooling in areas handled by the unit. He diagnosed the problems and left the site. On July 15, 1995, he returned to the site and replaced two fuses that he had diagnosed as being faulty on his previous visit. He disconnected the lower compressor, but did not open the air conditioner's disconnecting means. A ground fault occurred in the air conditioner circuit at the condenser motor. This energized the frame of the unit, which was ungrounded. (The unit's equipment grounding conductor had not been connected.) The employee was electrocuted when he contacted a bracket on the condenser fan motor with his right hand while he was holding a nut driver.