Abstract: A service worker and a supervisor for an air conditioning repair shop were performing a routine preseason preventive maintenance check on a rooftop condenser unit for an air conditioner. With the control cabinet cover removed, the service worker began taking current measurements. The top of this condensing unit (as the other similar units) stood about 0.6 meters (2 feet) above the tar-and-gravel-covered roof. To place the ammeter over the appropriate conductor with the air conditioner in operation, the employee had to maneuver his hands and arms around a 240-volt contact on a motor relay and two capacitors. He was in an unstable kneeling position and lost his balance, falling into the open cabinet. His right arm contacted the motor relay while his left arm was touching the grounded case of the unit. The employee was electrocuted.