As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT OUT AND OFF AND RETURNED TO PHX DUE TO AN ODOR COMING FROM AIR CONDITIONING VENTS IN THE BACK CABIN. FOUND AIR CONDITIONING RECIRCULATING FAN INOP. FOUND FAN RELAY R2-278 BAD. REPLACED RELAY, FAN NOW OPERATES NORMALLY. ALSO NOTED FLUID ACCUMULATION NEAR APU INLET. PERFORMED DUCT BURNOUT PROCEDURE PER OP 5088. CLEANED INLET SCREEN.