During Train Prep, 1556 encountered brak ~~~~~ Checked and confirmed abnormal air purge from soleniod coarse exhaust when EM to coast.Brakes slow release (3bar)Swap ACU from #1556 to #2556 fault and symptoms transfered.Replace ACU and carried out brakes cyclic/function test,satis.No abnormal air leak at brake frame.BCP within criteria.
#1556-ACU:
New s/n: 1244-106
Old s/n: 1047-079
Not: 2346425 raise.
Done by Joshua. 06/01/22