What was found
CREW REPORTED RECEIVING AN EICAS. LEFT PACK FAIL MESSAGE DURING TAXI. PILOT CYCLED THE LT PACK SWITCH,THE FAIL MESSAGE THEN CLEARED ITSELF. FAIL MESSAGE ILLUMINATED AGAIN AFTER T/O. THIS WAS ACCOMPANIED WITH AN AMBER LAV SMOKE EICAS. CREW REPORTED, NO EVIDENCE OF SMOKE OR FIRE COMING FROM THE LAV. JUST A SMELL OF FUMES. A/C RETURNED TO DENVER WITH NO FURTHER INCIDENTS. MX GROUND RAN THE A/C AND PERFORMED AN OP'S CHECK OF THE AIR CONDITIONING SYSTEM IAW AMM 21-21-00, NO DEFECTS NOTED. THE A/C WAS THEN RELEASED FOR SERV. THE CREW LATER REPORTED THAT THEY HAD AN EXTENDED TAXI PERIOD WITH THE ENGS IN GROUND IDLE AND A 12 KNOT TAIL WIND. SUBMITTER STATES, WE CAN ONLY SURMIZE THAT THE HEAVY TAIL WIND AND LO