Narrative:

At an intermediate cruise altitude one of the passengers came to the flight deck and advised us that 'the walls are too hot to touch.' I asked my first officer what the cabin temp setting was. He told me that it was in the manual position and the temperature selected to full cold. I asked him to don his oxygen mask and I transferred the autopilot to him. I left the flight deck to inspect the situation. I touched the walls where the ducting is located and found it too hot to leave my hand. I felt along the length of both walls and the result was the same. I advised the passengers that I was going to call maintenance and that we were most likely to divert. I returned to the flight deck and called dispatch and had them transfer me to maintenance. I spoke with maintenance and we agreed to divert to a nearby airport. I returned to pilot flying duties and advised my first officer that we are diverting to kind. I announced our intention to ATC to which they asked for the reason. I advised that we were diverting to kind as a precaution due to uncontrolled cabin temperature. Upon descent and power reduction the passenger informed me that the temperature was turning colder. Landing was uneventful.

Related reports:

Google
 

Original NASA ASRS Text

Title: A BE-400XP passenger informed the crew about an extremely hot cabin sidewall and after verifying the report the Captain diverted to a nearby airport for a precautionary landing.

Narrative: At an intermediate cruise altitude one of the passengers came to the flight deck and advised us that 'the walls are too hot to touch.' I asked my First Officer what the cabin temp setting was. He told me that it was in the manual position and the temperature selected to full cold. I asked him to don his oxygen mask and I transferred the autopilot to him. I left the flight deck to inspect the situation. I touched the walls where the ducting is located and found it too hot to leave my hand. I felt along the length of both walls and the result was the same. I advised the passengers that I was going to call Maintenance and that we were most likely to divert. I returned to the flight deck and called Dispatch and had them transfer me to Maintenance. I spoke with Maintenance and we agreed to divert to a nearby airport. I returned to pilot flying duties and advised my First Officer that we are diverting to kind. I announced our intention to ATC to which they asked for the reason. I advised that we were diverting to kind as a precaution due to uncontrolled cabin temperature. Upon descent and power reduction the passenger informed me that the temperature was turning colder. Landing was uneventful.

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.