As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT FL350 CABIN RATE OF CLIMB CONSTANTLY CLIMBS / DESCENDS +/- 500 FPM WITH OCCASIONAL SPIKE OF 1700 FPM. N1 STABLE AT 89.2, CABIN DIFF AT 7.8, CABIN ALT 7000FT. DUCT PRESS 45 PSI. NO CHANGE WHEN ALTN SELECTED. CABIN RATE SEEMS TO FOLLOW SLIGHT CHANGE IN RIGHT DUCT PRESSURE +/- 10 PSI RIGHT DUCT. GROUNDED - YES. REMOVED AND REPLACED RH TEMP CONTROL VALVE REF B737-900 AMM 21-51-10-400-801.