What was found
CAPTAIN REPORTED SMOKE ODOR IN THE CABIN. AIR CONDITIONING SYSTEM WAS SHUTDOWN AND APU DOORS WERE CHECKED, DETECTING A PLASTIC IN THE APU INLET. PLASTIC WAS REMOVED AND WATER SEPARATORS WERE REPLACED IAW MM 21-20-2, TESTED CORRECT. DURING BOARDING, CAPTAIN REPORTED AGAIN SMOKE ODOR IN THE CABIN, SO THE AIRCRAFT WAS SENT TO THE HANGAR. APU, WATER SEPARATORS AND PRIMARY AND SECONDARY HEAT EXCHANGERS OF BOTH SYSTEMS WERE REPLACED IAW MM 49-10-00, 21-20-2 AND 21-51-02, TESTED CORRECT.