Date: 201501
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Aircraft Heating System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL
Detector: Person Flight Attendant; Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed As Precaution; General Maintenance Action
Contributing factors: Aircraft; Weather; Procedure; MEL
Primary problem: Procedure

Narrative: Departed with an MEL'd Pack Flow Sensor. All MEL procedures were complied with. This included leaving the Hot Air p.b. switch in the OFF position. About 10 minutes after takeoff; Flight Attendant (F/A) called to say that cabin was cold. I adjusted the cabin temp selectors to a warmer position. As I monitored the cabin temp getting colder instead of warmer; I selected increasing amounts of warm temperature with no effect on the cabin temperature. A F/A called again to say the cabin was REALLY cold. By now we were level at FL310. The observed temperatures were 35 degrees F air going into the cabin with the cabin temp at 60 F and decreasing with all cockpit and cabin temp selectors selected to full hot. I initiated a call to dispatch and was patched through to maintenance to see if they had any ideas on how to fix our problem. I was told that they had nothing and that this particular MEL had been a problem before. In fact he added that this MEL should instead be an aircraft refusal. Armed with this knowledge I advised dispatcher that we would not be able to continue to [destination.] He suggested (two airports ahead of us). By now cabin temp was 54 F. [and his closest option] was still 450 miles away. I advised dispatch that my preference was for ZZZ; 120 miles directly south. Dispatch said [it was] my call and; at that time; the phone patch was lost. My First Officer (F/O) got the weather for ZZZ1 and ZZZ. ZZZ weather was good but ZZZ1 visibility at a mile and a half. With increasing cold and discomfort on the aircraft (by now the cockpit was uncomfortably cold); I decided safest course of action was diversion to ZZZ with overweight landing. Diversion was coordinated with dispatch over ACARS and then requested with ATC. Cabin was prepped for normal arrival. As we approached ZZZ; I received message from dispatch that gate would not be available for some time. I decided to enter holding to take a little extra time to review the overweight landing procedure in the QRH. I also called ops via VHF and found out that we had both an open gate and a mechanic standing by. With good weather; light winds; and a [very long] runway; I was confident that the overweight landing was the safest course of action. Out of extreme caution I had the F/O [advised ATC] and asked to have the equipment standing by. We made a very uneventful landing at 149400 pounds; touching down at less than 200 FPM. The taxi to the gate was normal. I will not take an airplane again with this MEL unless the flight is under an hour and then only in the summer.




Synopsis: An A320 dispatched with a deferred AC Pack Flow Sensor was unable to heat the aircraft interior and diverted to an enroute airport for maintenance.