What was found
FLT # 393, BOS-DEN(AIR TURNBACK TO BOS). CLIMBING OUT OF 5000 AIR BLEED 1 FAULT, ECAM ACTION COMPLETED, QRH FOLLOWED. PACK 1 AND 2 SHOWING AMBER XX AND PRESSURIZATION NOT WORKING PROPERLY. WE HELD ALTITUDE AT 10,000 FEET AND ATTEMPTED TO RESET PACKS WITH NO RESULTS. RETURN TO BOS ACCOMPLISHED; REF LOG PAGE 3332359 ITEM 1 & 2 AND LOG PAGE 3332360 ITEM 1 + 2 PERFORMED ENGINE HIGH POWER TO TEST BLEED SYSTEMS BOTH SYSTEMS OPERATED NORMAL WITH NO FAULTS. REMOVED + REPLACED ENG 1 FAV CONTROL THERMOSTAT REF AMM 36-11-43. C/W LEAK CHECK FAN THERMOSTAT IAW AMM 36-11-43. R&R LEFT ENGINE FAN AIR VALVE 9HA1 IAW AMM 36-11-54. OPERATIONAL / LEAK CHECK ACCOMPLISHED PER AMM 36-11-54, OPS CHECK OK