What was found
BOI FLIGHT NR 2385 - DURING CLIMB-OUT AT ABOUT 13,000, THE PRESSURE CONTROLLER STARTED TO INCREASE DIFFERENTIAL PRESSURE, BUT THEN STABILIZED. AT 23,000 ,THE DIFFERENTIAL STARTED AN ABNORMAL DECREASE IN PRESSURE. ATTEMPTED MANUAL CONTROL WITH NO AFFECT. PRESSURE WENT TO ZERO. AIRCRAFT RETURNED TO BOI. MAINTENANCE REMOVED AND REPLACED CABIN PRESSURE CONTROL PANEL (P/N 92147A020103, S/N 00111) IAW AMM 21-31-01. REMOVED AND REPLACED CABIN PRESSURE CONTROLLER IAW AMM 21-31-06. REMOVED AND REPLACED CARGO DOOR SEAL (P/N 52213) IAW 52-31-26. OPS CHECK NORMAL IAW 21-31-00. OCF WAS GOOD. AIRCRAFT RETURNED TO SERVICE.