What was found
ON DESCENT PASSING APPROX 12000-13000 FEET CABIN PRESSURE WARNING ILLUMINATED. CABIN RATE OF CLIMB INDICATOR WENT FROM -2000FPM TO +3000 IN ABOUT A SECOND. WE CONTINUED DESCENT AND WARNING EXTINGUISHED AROUND 10000 FT. CABIN DID NOT REGAIN PRESSURIZATION IN AUTO OR MANUAL. IPC AND E+A CHECKLISTS FOLLOWED. UPON ARRIVAL GROUND CREW NOTED THAT MAIN CABIN DOOR HANDLE WAS OPEN BY A FINGER TIP OR TWO. REMOVED FROM SERVICE. CDS SHOWED CP CONTROLLER FAIL. R&R CPC IAW Q400 AMM 21-31-06-000/400-801. OPS TEST GOOD. FUNCTIONAL TEST OF PRESS CONTROL IAW Q400 AMM 21-31-00-720-801. TESTS GOOD. NO WARNINGS AND NO FAULTS CURRENTLY. NO FURTHER DEFECTS AT THIS TIME. THIS CLEARS DEFECT 902686. PLACARDS REMOVED. MTX CONTROL NOTIFIED. AIRCRAFT RETURNED TO SERVICE.