B767-300 RETURNS TO DEP ARPT WHEN AN AIR CONDITIONING PACK FAILS PRIOR TO AN OCEANIC CROSSING.

Narrative

PRIOR TO DEP; I SPOKE WITH DISPATCHER ABOUT THE WRITE-UP HISTORY INVOLVING THE L PACK INOP THAT WAS CURRENTLY DEFERRED AND BEING WORKED ON BY MAINT. WE DISCUSSED THAT IF THE PROB RECURRED AFTER DEP; DEPENDING ON OUR POS AT THE TIME; I WOULD NOT TAKE THE PLANE ACROSS THE OCEAN. THE ACFT CAME FROM THE HANGAR WITH THE VALVE REPLACED AND THE DEFERRAL CLRED. ON CLBOUT THROUGH FL270 WE GOT THE L PACK OFF LIGHT EICAS. WE REQUESTED HOLDING WITH CTR WHILE WE PLANNED WITH DISPATCH AND MAINT CTLR AND RECEIVED A 'PPOS' HOLD. AFTER RUNNING CHKLISTS AND CONFERRAL; WE RETURNED TO ZZZ. IT WAS DECIDED BTWN THE CREW; MAINT CTLR; AND DISPATCH THAT AN OVERWT LNDG WOULD NOT BE AN ISSUE. WE LOWERED THE GEAR ON FINAL AND GOT A DOORS LIGHT AND CORRESPONDING EICAS ALONG WITH 3 GREEN LNDG GEAR DOWN LIGHTS. WE WENT AROUND AT 1500 FT FOR A RWY HDG GAR TO 2000 FT. AFTER AGAIN CONFERRING WITH MAINT CTLR AND DISPATCH; WE AGREED TO ACCOMPLISH THE LNDG WITH EQUIP STANDING BY. THIS UNEVENTFUL LNDG WAS MADE AT A LNDG WT OF 321K. THE DOORS LIGHT EXTINGUISHED ON LNDG AND WE TAXIED TO THE GATE. THE DOORS LIGHT WAS SUBSEQUENTLY FOUND TO BE A MISALIGNED SENSOR.