EMU 633/634 : MR unable to charge up. To ~~~~~ 3634 - AIR DRYER FAULT.  3634 Fault code 704 (Air Dryer Fault) on TIMS. Found air dryer unable to change over after 2 mins. Air dryer took 4 mins to change over. Found air leak on air dryer piston exhaust port. Air dryer replaced with new. Function tested with no abnormalities. Limited movement and depot shunting ok. #3634 Air dryer S/N : Old : 3514450237 New : 3515420311  Sarma/Anand/Sugu/Lee PT/Alan 45286