What was found
WITH AUTOPILOT ENGAGED PASSING 15,000 FT AIRPLANE PITCHED UP UNCOMMANDED. AFTER LEVELING AT 16,000 FT, RECONNECTED A/P. ALTITUDE LIGHT ALT ON FCP (CA AND F/O SIDES) WOULD NOT REMAIN ILLUMINATED. REMOVED AND REPLACED AUTO PILOT CONTROL PANEL IN CENTER CONSOLE. SYSTEM OPS CHECKS GOOD. P/N: 622-6684-006, S/N ON: 2804, S/N OFF: 8544