What was found
CREW REPORTED ON CLIMB, PASSING THROUGH FL180, AND AFTER ENCOUNTERING ICE, RECEIVED BLD1 OVERTEMP WARNING. ACFT RETURNED TO DEPARTURE WHERE IT LANDED WITHOUT INCIDENT. MX INSP ACFT AND PLACED THE BLEED SYS ON MEL 36-11-05, AND ACFT WAS APPROVED FOR RETURN TO SERVICE. LATER THAT DAY, ACFT RETURNED TO DEPARTURE, WHERE MX REMOVED AND REPLACED THE NR 1 FAN AIR THERMOSTAT, OPS TESTED WITH NO DEFECTS, AND THE ACFT WAS APPROVED FOR RETURN TO SERVICE.