What was found
CABIN ALTITUDE EICAS WARNING. CABIN ALTITUDE 10000 FT PILOTS REPORT EICAS WARNING AT FL330. AT THE TIME CABIN PRESSURE SHOWED 10000 WITH DIFFERENTIAL PRESSURE AT 7. ON DESCENT TO FL320 CABIN PRESSURE SHOWED 8500 WITH DIFFERENTIAL REMAINING AT 7. PERFORMED BITE CHECK OF THE CABIN PRESSURE CONTROLLERS, FOUND -AC POWER OFF- LIGHT ON DURING BITE. PERFORMED OPS CHK OF OUTFLOW VALVE, FOUND ERRATIC INDICATION OF OUTFLOW VALVE POSS INDICATOR AT OVERHEAD PANEL, INDICATOR QUIVERING WHILE VALVE OPENING & CLOSING. IAW FIM 21-31 TREE 803. AMM 21-31-04. R & R OUTFLOW VALVE ACTUATOR ASSY, IAW AMM 21-31-04. POST INSTALLATION TEST OK.