Narrative:

About 5000' AGL; we got amber auto fail light and a green standby light. Seeing the green standby light; we continued the climb and began checking the QRH and gauges. We noticed a cabin altitude of around one to two thousand; a normal differential pressure and the confusing one was the cabin rate was showing a descending cabin of around 500' a minute; but we were climbing at around 4000' a minute and the cabin was not climbing looking at this gauge. Believing we were still pressurizing because of the stby light; we continued to climb. I was flying and the captain was in the QRH. Passing through around 13;000'; I began to feel tingling in my arms and legs. Having experienced symptoms of hypoxia before; I immediately donned my O2 mask and started a descent. I told the captain we were not pressurizing and to get his mask on; within a few seconds the tingling was gone. The captain noted the cabin altitude per the gauge had just dropped to zero; when it should have been at around 3000'; or at least climbing with us; a completely different from what it should have been doing. I coordinated with ATC a descent to 10;000'. We reached an altitude of around 13;800 feet as a top of climb. The captain decided we would return to departure airport. I coordinated again with ATC while the captain talked to the F/as. We removed our masks at 10;000'; and returned uneventfully. No passenger issues were noted. The next day I spoke with maintenance control and they said it was a pressure control failure. They replaced it that night and the aircraft was back in service. I was once told in training that if you have a green light on the pressurization panel; 'you're good.' obviously this is not true. It seems that at lower altitudes it's hard to recognize a dual pressure control failure. We probably should have leveled off at 6000' just to make sure we were actually pressurizing.

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Original NASA ASRS Text

Title: B737-300 Flight Crew experiences an AUTO Fail with a green STBY light climbing through 5000 feet. The QRH is consulted and the crew continues climbing with normal pressurization indications except for the cabin indicating a descent. At 13000 feet the First Officer believes he is experiencing hypoxia and dons his oxygen mask and noses over. Flight returns to departure airport uneventfully.

Narrative: About 5000' AGL; we got amber Auto Fail light and a green Standby light. Seeing the green Standby light; we continued the climb and began checking the QRH and gauges. We noticed a cabin altitude of around one to two thousand; a normal differential pressure and the confusing one was the cabin rate was showing a descending cabin of around 500' a minute; but we were climbing at around 4000' a minute and the cabin was not climbing looking at this gauge. Believing we were still pressurizing because of the STBY light; we continued to climb. I was flying and the Captain was in the QRH. Passing through around 13;000'; I began to feel tingling in my arms and legs. Having experienced symptoms of hypoxia before; I immediately donned my O2 mask and started a descent. I told the Captain we were not pressurizing and to get his mask on; within a few seconds the tingling was gone. The Captain noted the cabin altitude per the gauge had just dropped to zero; when it should have been at around 3000'; or at least climbing with us; a completely different from what it should have been doing. I coordinated with ATC a descent to 10;000'. We reached an altitude of around 13;800 feet as a Top of Climb. The Captain decided we would return to departure airport. I coordinated again with ATC while the Captain talked to the F/As. We removed our masks at 10;000'; and returned uneventfully. No Passenger issues were noted. The next day I spoke with Maintenance Control and they said it was a pressure control failure. They replaced it that night and the aircraft was back in service. I was once told in Training that if you have a green light on the pressurization panel; 'you're good.' Obviously this is not true. It seems that at lower altitudes it's hard to recognize a dual pressure control failure. We probably should have leveled off at 6000' just to make sure we were actually pressurizing.

Data retrieved from NASA's ASRS site as of July 2013 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.