What was found
FLT 1024 - MKE-CVG - DURING FLIGHT, THE CABIN ALT HI ANNUNCIATOR ILLUMINATED AT FL 230. THE FLIGHT CREW NOTED THE CABIN ALTITUDE WAS AT FL 100 AND CLIMBING. SO THE CREW DEPLOYED THE OXYGEN MASKS, DIVERTED TO FWA AND MADE AN UNEVENTFUL LANDING. THE CREW CONTACTED MAINTENANCE AND THAN FERRIED THE A/C BACK TO MKE. MAINTENANCE INSPECTED THE SYSTEM AND REPLACE THE PRECOOLER AND THE PRSOV. MAINTENANCE OP CHECKED THE SYSTEM AND RETURNED THE A/C TO SERVICE. (M)