What was found
FLT 503 - MCO - AUTO-PILOT WILL NOT HOLD ALTITUDE IN CRUISE, AT FL 290 OR 310. AIRCRAFT CLIMBS AT A STABLE 300 FPM WITH THE VERTICAL SPEED WHEEL IN THE DETENT. ASSIGNED TO DMI. DMI NR 00294 IAW MEL 22-16-6 NOTIFIED. MAINTENANCE CONTROL AND PLACARDED CONTROLLER AS REQUIRED. RAN TESTS ON PITCH COMPUTER IAW DC-9 MM 22-10-00. CHECKS GOOD. SYSTEM GROUND CHECKS GOOD, CLEARS DMI NR 00294. (M)