From Dave Schneebeck,
I was a second officer on a 320 flying from SEA to MIA on a charter flight. About 2:30 after takeoff the cabin pressure began to dive and climb rapidly. I went to manual control and that seemed to slow the dives and climbs but not sufficiently. Dispatch was notified about the problem and they in turn connected us to maintenance. I was instructed to go behind the 2nd officers panel, remove a protective covering, and jiggle some wires carefully. CAREFULLY, because the voltage in the wires surrounding the area where I was "jiggling" were 600 volts. Needless to say we diverted to MSP and got a different aircraft. Once on the ground I was told by a mechanic that they wouldn't work in the area where I was jiggling wires unless all of the power was removed from the aircraft and the battery switch turned off. I didn't want to do that, again!!!