What was found
CLIMBING THROUGH FL210 RECEIVED ANTI ICE WARNING WITH OVERHEAT INDICATION, C/W QRH MESSAGE PERSISTED. AIR RETURNED TO ROC PER QRH, FLAPS 20 REF 45+30 KNOTS (SPEED WAS 169) NO THRUST REVERSERS AVAILABLE/FULL BRAKING. TEMPS AT GATE 8-10-5-5 LANDING WEIGHT 46,000 LBS. ANTI ICE DUCT SWITCH LIGHT OVERHEAT SECTION ILLUMINATED (WING), NO DUCT FAIL LIGHTS ILLUMINATED ON ANY SWITCH. WARNING CLEARED IN FLIGHT APPROXIMATELY 5-10 MINUTES AFTER RUNNING QRH. WHEN WARNING WAS RECEIVED 14TH STAGE SOV INDICATED OPEN, 10TH STAGE SOV INDICATED OPEN, APU LCV INDICATED CLOSED, ISOLATION VALVE CLOSED.