EMU 531/532 # 2531 ACU leak. ~~~~~ EMU 531/532 - #2531 ACU leak.  2531 ACU AF SV ticking (ACU air leak found). Replaced ACU with available spare - Done. Security/function check - OK. Depot shunting & no fault occurred. 2531 ACU S/N : OLD : 1002/002    NEW : 1240/099  KA  44068