What was found
AT CRUISE AT 350, CABIN PRESSURE FLUCTUATED NONSTOP +/- 500' FPM ENTIRE FLIGHT. NOTICEABLE IN EARS AND GAUGE. CABIN HELD STEADY AT 7000' AND 7.8 PSID. DESCENDED LATER TO 310 AND FLUCTUATIONS CONTINUED. GROUNDED-YES. CABIN PRESS CONTROL NR 1 AND NR 2 BITE, PER B737-900 FIM 21-31 TASK 801 SHOWED NO FAULTS AND SYSTEM TEST PASSED. PACK FLOW TEMP CONTROL NR 1 AND NR 2 BITE, PER FIM 21-62 TASK 801 SHOWED NO FAULTS. ACCOMPLISHED T/S, PER FIM 21-33 TASK 802. FOUND RIGHT PACK TEMP CONTROL VALVE V141 OPERATING ABNORMALLY, VALVE WAS MAKING BROAD ADJUSTMENTS TO PACK TEMP AND RIGHT PACK APPEARED TO BE FLUCTUATING. R & R AND TESTED RIGHT PACK TCV, PER B737-900 AMM 21-51-10-000-801/AMM 21-51-10-400-801. OPERATIONS NORMAL, NO LEAKS NOTED.