A B737-800 ON CLB AT 9000 FT DECLARED AN EMER AND RETURNED TO ZZZ DUE TO L WING BODY OVERHEAT WARNING ON. R WING BODY OVERHEAT PREVIOUSLY DEFERRED AS INOP.

Narrative

RIGHT WING BODY OVERHEAT ILLUMINATED ON TAXI OUT; LIGHT WAS EXTINGUISHED AS PER CHECKLIST RE-ILLUMINATED AND WE CONFIRMED WITH MAINT. LIGHT WAS EXTINGUISHED AGAIN AS PER CHECKLIST PROC; INITIATED FLIGHT WITH APU OFF; R ENG BLEED OFF; R PACK OFF; AND ISOLATION VALVE CLOSED. AT 9000 FT ON CLB OUT; THE L WING BODY OVERHEAT CAME ON. WE POWERED BACK ON L ENG; DECLARED AN EMER; AND RETURNED TO ZZZ. GOT TO GO; NEW ACFT AT GATE; AND INTO MIN REST AT ZZZ1. SUPPLEMENTAL INFO FROM ACN 628687: DURING TAXI OUT; R WING BODY OVERHEAT LIGHT ILLUMINATED. WE FOLLOWED CHECKLIST AND IN 2 MINS THE LIGHT WENT OUT. THE ACFT WAS EXTREMELY WARM; WE RESET THE ISO-VALVE; BLEED VALVE AND TUNED ON R PACK TO HELP COOL ACFT. OUR DEP WAS DELAYED DUE TO DEPS; 10 MINS LATER THE SAME R WING BODY OVERHEAT LIGHT ILLUMINATED AGAIN. WE RE-DID THE CHECKLIST; NOTIFIED MAINT OF OUR PROB AND DISPATCH OK'D THE FLT TO CONTINUE ON 1 BLEED/1 PACK 25000 FT RESTRICTION AN NO ICING ENRTE. WE DEPARTED AND CLBING OUT OF 9000 FT; THE L WING BODY OVERHEAT ILLUMINATED AND I IMMEDIATELY DECLARED AN EMER. WE HEADED TO ZZZ AND FO TOLD THE FA'S VIA INTERPHONE WE WERE RETURNING AND TO PREPARE FOR IMMEDIATE RETURN. AS FO WORKED THE CHECKLISTS; I CALLED FOR FIRE TRUCKS TO BE THERE; FEELING THIS WAS A VERY HIGH POTENTIAL OF A 'REAL BLEED LEAK.' ON A 9 MILE FINAL; I MADE A PA TO STATE TO THE CREW TO PREPARE FOR AN EMER LNDG. WE LANDED WITH A TAILWIND; AND GOT THE OK TO TAXI TO A GATE. CALLBACK CONVERSATION WITH RPTR ACN 628688 REVEALED THE FOLLOWING INFO: THE RPTR STATED IT APPEARED ODD THAT TWO SEPARATE SENSING LOOPS WOULD FAIL AND GIVE A FALSE WARNING. THE RPTR SAID ON THE GND; MAINT MADE A BITE CHECK OF THE SYSTEM AND FOUND THE CTL UNIT HAD FAILED. THE RPTR STATED THE CTL UNIT WAS REPLACED AND BOTH SENSING LOOPS CHECKED OK. THE RPTR SAID THE AIRPLANE WAS A B737-800.