Narrative:

During the final segment of the climb the flight attendants alerted us that the cabin was a little warm and passengers were complaining. Cabin temperature at the time was about 79 degrees. We took control of the cabin temperature and set it to full cold. We left this configuration for about half of the cruise period of the flight. The temperature continued to rise slowly during this time at about 1 degree every 10 to 15 minutes. Later during cruise we tried recirculation fans in the off and on position with little affect. We also gave control back to the flight attendant panel for awhile with no affect. Dispatch was alerted to our difficulty and we asked for some advice from maintenance control. Maintenance advised us to set the temperature controller to the cold position.with the temperature continuing to slowly rise we discussed a couple of other options. One was to try the deferred pack and the other was to descend and try the APU bleed. We asked center about an early descent to help us with some cabin temperature issues and after we explained our situation they declared our flight an emergency and gave us vectors direct to ZZZ. We alerted dispatch of our intention to descend early to try the APU fix and continued on.with temperatures starting to get close to 90 degrees in the descent I decided to try the deferred pack to lower the temperature. Using the deferred pack gave us an initial drop in temperature right away but it slowly began to creep up again a little later and I turned it off. Reaching 14000 ft we turned on the APU and turned off bleeds one and two. In this configuration we utilized pack one by itself and also pack one and two together. Neither option lowered the temperature. The temperature maintained steady around 90 degrees near the end of the flight. I maintained communication with the flight attendant's during this whole process who advised the passengers were very warm but no one was in distress or needed medical attention. We landed the flight without incident in ZZZ and the rescue trucks followed us to the gate. No passengers required assistance off the aircraft.I should have used the radio to communicate with dispatch instead of ACARS only and had a more detailed conversation with them about the issues. Even though I have never received any real help from maintenance in the past during inflight troubleshooting other than 'follow the QRH and call us on the ground' I should have pressed them harder than the initial question I asked them and maybe this time could have been different. Aside from the fact that I had emergency authority to try whatever I could to fix the problem; it is very unlikely that I will use a deferred item in the future to try and fix a problem and instead divert more quickly and have maintenance fix the problem.

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Original NASA ASRS Text

Title: An EMB 170 Flight Crew elected to divert for maintenance when they were unable to control an uncommanded rise in cabin temperature.

Narrative: During the final segment of the climb the Flight Attendants alerted us that the cabin was a little warm and passengers were complaining. Cabin temperature at the time was about 79 degrees. We took control of the cabin temperature and set it to full cold. We left this configuration for about half of the cruise period of the flight. The temperature continued to rise slowly during this time at about 1 degree every 10 to 15 minutes. Later during cruise we tried recirculation fans in the off and on position with little affect. We also gave control back to the Flight Attendant panel for awhile with no affect. Dispatch was alerted to our difficulty and we asked for some advice from Maintenance Control. Maintenance advised us to set the temperature controller to the cold position.With the temperature continuing to slowly rise we discussed a couple of other options. One was to try the deferred pack and the other was to descend and try the APU bleed. We asked Center about an early descent to help us with some cabin temperature issues and after we explained our situation they declared our flight an emergency and gave us vectors direct to ZZZ. We alerted Dispatch of our intention to descend early to try the APU fix and continued on.With temperatures starting to get close to 90 degrees in the descent I decided to try the deferred pack to lower the temperature. Using the deferred pack gave us an initial drop in temperature right away but it slowly began to creep up again a little later and I turned it off. Reaching 14000 ft we turned on the APU and turned off bleeds one and two. In this configuration we utilized pack one by itself and also pack one and two together. Neither option lowered the temperature. The temperature maintained steady around 90 degrees near the end of the flight. I maintained communication with the Flight Attendant's during this whole process who advised the passengers were very warm but no one was in distress or needed medical attention. We landed the flight without incident in ZZZ and the rescue trucks followed us to the gate. No passengers required assistance off the aircraft.I should have used the radio to communicate with Dispatch instead of ACARS only and had a more detailed conversation with them about the issues. Even though I have never received any real help from Maintenance in the past during inflight troubleshooting other than 'follow the QRH and call us on the ground' I should have pressed them harder than the initial question I asked them and maybe this time could have been different. Aside from the fact that I had emergency authority to try whatever I could to fix the problem; it is very unlikely that I will use a deferred item in the future to try and fix a problem and instead divert more quickly and have Maintenance fix the problem.

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.