What was found
DURING DESCENT, OUTFLOW VALVE FLUCTUATED TOWARDS OPEN AT LARGE INTERVALS ON 3 SEPARATE OCCASIONS (23,000' 16,500' & 10,000'). THIS RESULTED IN CABIN CLIMB RATES OF 3000 FPM AND PRESSURE DIFFERENTIALS THAT COULD BE FELT IN THE PILOTS EARDRUMS. NO CAUTION LIGHTS OBSERVED.: PERFORMED SYSTEM TEST, NO FAULTS NOTED AT THIS TIME - A/C OK FOR SERVICE. REF FIM 21-31 TASK 801 AND AMM 21-31-00.