What was found
DURING CLIMBOUT, CABIN FAILED TO STABILIZE AT 5200FT. CABIN ALTITUDE FOR CRUISE FLT 340 AT CRUISE FLT (340), CABIN ALT EXCEEDED 10000FT. DESCENT INITIATED AND MANUAL PRESSURIZATION WAS SELECTED AND OUTFLOW VLV WAS FULL CLOSED, CARGO HEAT VLV WAS CLOSED, 2 PACKS WERE OPERATING AND THE CABIN REMAINED UNCONTROLLABLE COULD NOT DECREASE CABIN ALT UNTIL DESCENT BELOW 17000FT. CABIN ALT AND ACFT ALTITUDE EQUALIZED AT 10000FT. DURING PRESSURIZATION TROUBLESHOOTING FOUND RT PACK SWITCH FAULTY. REPLACED ACFT AND PRESSURIZATION ASSY MODULE IAW MM REF 31-00-011-4. DECAY CHK IAW JRH GOOD. PANEL OPS CHK GOOD.