What was found
AIR CONDITIONING SYSTEM PRODUCED A DIRTY SOCK ODOR. REMOVED LEFT AND RIGHT WATER SEPARATOR COALESCER BAG AND INSTALLED NEW. COMPLIED WITH CMP 215005 AIR CONDITIONING SYSTEM OPS TEST WITH NO DEFECTS NOTED. THERE IS STILL AN ODOR PRESENT ONLY WHEN THE APU IS RUNNING THE A/C PACKS. ISOLATED LEFT AND RIGHT PACK WITH NO DIFFERENCE. STARTED LEFT AND RIGHT ENGINES AND OPERATED BOTH PACKS FOR 30 MINUTES AND ODOR DISAPPEARED. SELECTED APU AS AIR SOURCE AND ODOR IMMEDIATLY RETURNED. CHECKED BOTH PACKS FOR PROPER OPERATION WITH NO DEFECTS FOUND. REMOVED APU AND INSTALLED A REPAIRED UNIT. COMPLIED WITH CMP MSG3 490052 OPS TEST. OPS AND LEAK CHECKED GOOD. CHECKED BOTH PACKS FOR PROPER OPERATION WITH NO DEFECTS FOUND.