What was found
CMH-DIVERTED FLIGHT- ON CLIMBOUT THE CABIN PRESSURE RATE FLUCTUATED FROM -600 FPM TO +1400 FPM. PRESSURIZATION SYSTEM 1 FAILED. AUTO SWITCH TO SYSTEM 2 AND CABIN PRESSURE FLUCTUATIONS CONTINUED. THE OUTFLOW VALVE CYCLED CONTINOUSLY, EVEN IN LEVEL FLIGHT AT FL 280. THE BLEED PAGE SHOWED N1 PACK PRESSURE PULSING BETWEEN 8 PSI AND 26 PSI. WITH NR 1 PACK OFF THE CABIN STABILIZED AND THE AIRCRAFT DIVERTED TO CMH. IN CMH MX REPLACED THE CABIN OUTFLOW VALVE AND OPERATIONAL CHECKS WERE GOOD. ON A SUBSEQUENT FLIGHT THE SAME DISCREPANCY WAS REPORTED AND THE CREW OPENED THE CROSSBLEED AND TURNED THE NR 1 BLEED OFF AND THE SYSTEM OPERATED NORMAL. IN PHX MAINTENANCE TROUBLESHOT THE PROBLEM.