What was found
AIRCRAFT WAS GROUNDED: ALTERNATE PRESSURIZATION CONTROLLER SURGES DURING DESCENT BETWEEN 300FT/MIN UP TO OVER 800 FT/MIN. REPLACED CABIN PRESSURE CONTROLLER #2 PER AMM 21-31-01 AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK. ALSO REPLACED RIGHT HAND PACK TEMPEATURE CONTROL VALVE PER AMM 21-51-10 AS A PRECAUTION. ACCOMPLISHED A SATISFACTORY LEAK AND OPERATIONAL CHECK (NOTE: A SIMILAR ISSUE WITH THE CABIN PRESSURTIZATION THAT OCCURED ON THE SAME DAY. THE REPLACEMENT OF CABIN PRESSURE CONTROLLER #2 AND THE RIGHT HAND PACK TEMPEATURE CONTROL VALVE CORRECTED THAT ISSUE ALSO.