What was found
WHILE CLIMBING THROUGH 20,000 FT , THE CREW RECEIVED A CAUTION MESSAGE FOR A LT WING OVERHEAT. AFTER FOLLOWING THE QRH, 14TH STAGE BLEED WAS SHUT OFF AND ISOLATION VALVE OPENED WITH THE RT BLEED SUPPLYING, THE LT, CREW THEN GOT A MESSAGE FOR A RT WING OVERHEAT. AT THIS POINT THE DECISION WAS MADE TO RETURN TO BASE. DEFECT 936967 CREATED LT WING OVERHEAT INFLIGHT (RESOLVED ON W/O: 252609 TASKCARD: NR-00001) LT WING ANTI-ICE VALVE REPLACED. PN 3214442-4 ACFT GROUND RUNS CARRIED OUT AND WING ANTI-ICE SYS OPS CHECKED AT TAKEOFF THRUST FOR 2 MINUTES - NO FAULTS FOUND-GROUND CHECKS SERVICABLE.