Narrative:

Very early we lost the cabin heater; but decided with the length of flight we would make the flight. It was bitter cold in the cabin. Also the two panel mount GPS unit screens started hazing over becoming difficult to read. At that point I requested from a deviation to go to [a nearby airport]. At that point we were given radar vectors and at some point a new altitude. We had been at 7;000 ft. As we descended we were in VFR conditions. [ATC] told me to expect radar vectors for the ILS rwy 23 and I was cleared down to 2;700 ft. Trying to load the ILS was almost impossible as by this time the GPS screens were almost unreadable. I was flying on autopilot; descending; trying to load the ILS and visually searching for the airport. It was during this time the auto pilot failed and not noticing it at first; I descended below the assigned altitude of 2;700 ft. I remember being at 2;400 ft and I might have been momentarily a little lower. With the help and guidance from [ATC] I did recapture my altitude and I was able to spot the airport for a visual approach and landing.on the ground I reset the cabin heater (can only be done on the ground) but elected to spend the night and fly to [our destination] in the morning when VFR conditions were forecasted. We wanted VFR daytime flight conditions to check out the avionics. On friday morning we had clear skies and we flew back VFR. The heater worked and with a warm cabin; the GPS units as well as the autopilot worked perfectly.

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Original NASA ASRS Text

Title: PA31 pilot reported while flying during extreme cold conditions; an inoperative cabin heater caused the cabin of a twin piston aircraft to become abnormally cold. Pilot stated this resulted in difficulty reading the GPS screens; failure of the autopilot; and the need for ATC assistance with a diversion.

Narrative: Very early we lost the cabin heater; but decided with the length of flight we would make the flight. It was bitter cold in the cabin. Also the two panel mount GPS unit screens started hazing over becoming difficult to read. At that point I requested from a deviation to go to [a nearby airport]. At that point we were given radar vectors and at some point a new altitude. We had been at 7;000 ft. As we descended we were in VFR conditions. [ATC] told me to expect radar vectors for the ILS Rwy 23 and I was cleared down to 2;700 ft. Trying to load the ILS was almost impossible as by this time the GPS screens were almost unreadable. I was flying on autopilot; descending; trying to load the ILS and visually searching for the airport. It was during this time the auto pilot failed and not noticing it at first; I descended below the assigned altitude of 2;700 ft. I remember being at 2;400 ft and I might have been momentarily a little lower. With the help and guidance from [ATC] I did recapture my altitude and I was able to spot the airport for a visual approach and landing.On the ground I reset the cabin heater (can only be done on the ground) but elected to spend the night and fly to [our destination] in the morning when VFR conditions were forecasted. We wanted VFR daytime flight conditions to check out the avionics. On Friday morning we had clear skies and we flew back VFR. The heater worked and with a warm cabin; the GPS units as well as the autopilot worked perfectly.

Data retrieved from NASA's ASRS site 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.