A line mechanic reports about a B737-300 aircraft that returned to field due to uncontrollable cabin...

Attributes
ACN	974682
Time
Date	201109
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Night
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	Technician
Qualification	Maintenance Airframe Maintenance Powerplant
Events
Anomaly	Aircraft Equipment Problem Critical Inflight Event / Encounter Other / Unknown

Narrative:

Removed and replaced (right/right) overhead pressurization control module on aircraft X. Aircraft was terminated over the night. I did everything by the maintenance manual (M/M). In the morning; next day when the aircraft left the gate; [flight crew] had to perform air return back due to uncontrollable cabin pressure. When fellow technician troubleshot the system he found two wires behind the pressure indication (psi) control panel [that] were chafing; which could have been chafing for long time. The right/right [of the control panel] caused the problem for wiring to pop up. That could have happened when the airframe vibration was induced by aircraft movement; either on the ground or during flight.

Original NASA ASRS Text

Title: A Line Mechanic reports about a B737-300 aircraft that returned to field due to uncontrollable cabin pressurization after he had changed the pressure control panel on the P-5 overhead panel. Troubleshooting later discovered two chafed wires behind the pressure indication panel.

Narrative: Removed and Replaced (R/R) overhead pressurization control module on aircraft X. Aircraft was terminated over the night. I did everything by the Maintenance Manual (M/M). In the morning; next day when the Aircraft left the gate; [flight crew] had to perform air return back due to uncontrollable cabin pressure. When fellow Technician troubleshot the system he found two wires behind the pressure indication (PSI) control panel [that] were chafing; which could have been chafing for long time. The R/R [of the control panel] caused the problem for wiring to pop up. That could have happened when the airframe vibration was induced by aircraft movement; either on the ground or during flight.

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.

A line mechanic reports about a B737-300 aircraft that returned to field due to uncontrollable cabin pressurization after he had changed the pressure control panel on the P-5 overhead panel. Troubleshooting later discovered two chafed wires behind the pressure indication panel.