What was found
APU ON & RUNNING, ASSOCIATED AIR SWITCHES IN CORRECT POSITION BUT ZERO AIR FLOW TO & FROM EITHER LEFT OR RIGHT PACK. ACFT GROUNDED. APU FAULTS 49-61259, 49-61262, & 49-52270. R & R ECU IAW AMM 49-61-12/401. PERFORMED OPS CHECK OF APU. WITH APU ON CHECKED CURRENT FAULTS, NO FAULTS NOTED. CHECKED DELTA P ON INPUT MONITORING AND SAW AN INDICATION IAW AMM 49-61-12. TURNED ON APU BLEED AND RAN BOTH PACKS. BLEED VALVE OPENED NORMALLY AND BOTH PACKS OPERATED NORMALLY IAW AMM 21-00-00. APU OPS CHECKED NORMAL.