TC reported air-con fault. Unable to reset. Staff(CTH) checked and confirmed that Front M1 car set # 2 air-con faulty. Reset - ok. Car was cooling. TC reported a ir-con fault. Unable to reset. Staff(CTH) checked and confir ~~~~~ TC reported air-con fault. Unable to res #1657 FC-628,A/C2 not running event door open.Further check a/c 2-1 zero freon,top up freon check CCU was new unit and no sign freon leak ,monitoring 2 hrs LP=40psi,HP=100psi pressure steady.A/C 2-2 CCU LP char coupling heavy freon leak.C/O coupling copper ring and top up freon monitor no leaking and LP=40psi & HP=100psi steady.Cooling found ok. Done by Rizman/Koh. 22/05/23