Narrative:

Flight from ZZZ to ZZZ1. At 13000 ft had pressurization 'automatic fail' light illuminate. System switched to standby automatically, as advertised. QRH checklist were used as per SOP and system switched to 'standby.' cabin was at sea level and started a descent in cabin attendant pressurization at 4000 FPM. We asked to level at 14000 ft from center and approved. Differential pressure was exceeding limits. We asked to descend and told to standby. Passengers ears were in distress. We declared an emergency to get lower altitude. Pressure switched to manual in attempt to open outflow valve. Differential pressure reached 9.0 and cabin attendant was well below sea level. While in descent to 5400 ft cabin attendant started climb at 4000 FPM until 7.0 differential at which point cabin attendant started to pressure at 4000 FPM. Cabin attendant continued to cycle until short final. Could not get outflow valve to open in either manual mode. A visual approach was executed to ZZZ1. Flight attendants and passengers briefed and normal landing made. At approximately 1000 ft AGL the forward outflow valve opened depressurizing aircraft. Medical personnel met aircraft at gate for passengers. I believe pressurization controller failed in all modes with outflow closed. This caused aircraft to pressure to limits until pressure relief valves to open repeatedly causing our severe pressure surges. Callback conversation with reporter revealed the following information: the reporter stated the airplane continued to pressurize and the over pressure relief valve was cycling open and closed causing distress to the passengers and crew. The reporter said nothing in the quick reference handbook would relieve the pressure as all pressurization control was lost and control of the outflow valve was lost. The reporter stated when on the ground maintenance removed the cabin attendant pressure controller and discovered liquid coming from the box.

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Original NASA ASRS Text

Title: A B737-200 IN CLB AT 14000 FT DECLARED AN EMER AND DSNDED DUE TO TOTAL FAILURE OF THE PRESSURIZATION SYS CAUSED BY CTLR FAILURE.

Narrative: FLT FROM ZZZ TO ZZZ1. AT 13000 FT HAD PRESSURIZATION 'AUTO FAIL' LIGHT ILLUMINATE. SYSTEM SWITCHED TO STANDBY AUTOMATICALLY, AS ADVERTISED. QRH CHKLIST WERE USED AS PER SOP AND SYSTEM SWITCHED TO 'STANDBY.' CABIN WAS AT SEA LEVEL AND STARTED A DSCNT IN CAB PRESSURIZATION AT 4000 FPM. WE ASKED TO LEVEL AT 14000 FT FROM CENTER AND APPROVED. DIFFERENTIAL PRESSURE WAS EXCEEDING LIMITS. WE ASKED TO DSND AND TOLD TO STANDBY. PASSENGERS EARS WERE IN DISTRESS. WE DECLARED AN EMER TO GET LOWER ALTITUDE. PRESSURE SWITCHED TO MANUAL IN ATTEMPT TO OPEN OUTFLOW VALVE. DIFFERENTIAL PRESSURE REACHED 9.0 AND CAB WAS WELL BELOW SEA LEVEL. WHILE IN DSCNT TO 5400 FT CAB STARTED CLB AT 4000 FPM UNTIL 7.0 DIFFERENTIAL AT WHICH POINT CAB STARTED TO PRESSURE AT 4000 FPM. CAB CONTINUED TO CYCLE UNTIL SHORT FINAL. COULD NOT GET OUTFLOW VALVE TO OPEN IN EITHER MANUAL MODE. A VISUAL APCH WAS EXECUTED TO ZZZ1. FLIGHT ATTENDANTS AND PASSENGERS BRIEFED AND NORMAL LNDG MADE. AT APPROX 1000 FT AGL THE FORWARD OUTFLOW VALVE OPENED DEPRESSURIZING ACFT. MEDICAL PERSONNEL MET ACFT AT GATE FOR PASSENGERS. I BELIEVE PRESSURIZATION CTLR FAILED IN ALL MODES WITH OUTFLOW CLOSED. THIS CAUSED ACFT TO PRESSURE TO LIMITS UNTIL PRESSURE RELIEF VALVES TO OPEN REPEATEDLY CAUSING OUR SEVERE PRESSURE SURGES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE CONTINUED TO PRESSURIZE AND THE OVER PRESSURE RELIEF VALVE WAS CYCLING OPEN AND CLOSED CAUSING DISTRESS TO THE PASSENGERS AND CREW. THE RPTR SAID NOTHING IN THE QUICK REFERENCE HANDBOOK WOULD RELIEVE THE PRESSURE AS ALL PRESSURIZATION CTL WAS LOST AND CTL OF THE OUTFLOW VALVE WAS LOST. THE RPTR STATED WHEN ON THE GND MAINT REMOVED THE CAB PRESSURE CTLR AND DISCOVERED LIQUID COMING FROM THE BOX.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.