A B737-400's auto pressurization mode malfunctioned at FL190 in the climb. An emergency was declared...

Narrative:

Passing through FL190 pressurization began degrading in auto mode. The climb was discontinued but the standby mode did not correct the problem so we requested a descent. ATC was unable to comply; due to lower traffic. The cabin warning horn began to sound. An emergency was declared and ATC cleared aircraft to a lower altitude. Upon reaching a lower altitude; and regaining control of cabin altitude; ATC was informed emergency no longer existed. The emergency was canceled. The crew requested a holding pattern then contacted dispatch and maintenance. It was decided the flight could be safely diverted to an enroute airport and the flight then continued to the diversion airport.

Original NASA ASRS Text

Title: A B737-400's Auto Pressurization Mode malfunctioned at FL190 in the climb. An emergency was declared as the Cabin Altitude Warn Horn sounded. After descending and controlling the cabin the emergency was terminated and the aircraft continued to a diversionary airport for maintenance.

Narrative: Passing through FL190 pressurization began degrading in Auto Mode. The climb was discontinued but the Standby Mode did not correct the problem so we requested a descent. ATC was unable to comply; due to lower traffic. The Cabin Warning Horn began to sound. An emergency was declared and ATC cleared aircraft to a lower altitude. Upon reaching a lower altitude; and regaining control of cabin altitude; ATC was informed emergency no longer existed. The emergency was canceled. The crew requested a holding pattern then contacted Dispatch and Maintenance. It was decided the flight could be safely diverted to an enroute airport and the flight then continued to the diversion airport.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	846651
Time
Date	200908
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

A B737-400's auto pressurization mode malfunctioned at FL190 in the climb. An emergency was declared as the cabin altitude warn horn sounded. After descending and controlling the cabin the emergency was terminated and the aircraft continued to a diversionary airport for maintenance.