I purchased this unit in June 2012, ac worked fine. The problems began when I had to turn on the heat. This unit was very noisy, to the point I could hear it kick on and shift modes in several rooms of my home, was sometimes awaken by the noise at night, and my neighbor also complained of the noise. The installer explained the shift into defrost mode but his explanation didn't fit the noises the unit was making. Sometimes the unit would make a very loud noise when trying to start, decrease in noise level, and start again. This could happen 3 times within one cycle. The noise sounded like a motor straining. The installer made numerous trips out to try to catch the noise without any luck. Finally, they installed a sound blanket which reduced the noise somewhat but did not address the problem with the straining motor. I have also noticed the unit has moved 4-6 inches so I am guessing there is significant vibration probably associated with the straining motor. On the installer's last trip out, they also informed me the unit would not function properly below 30 degrees and that I should manually switch the unit to "emergency heat". This part of the country often sees temperatures in the teens and below during the coldest months. If that had been disclosed prior to purchase I would have asked of a different model. To date the problems remain unresolved. I think I just have to write this experience off and buy another unit – too bad since I'm on a fixed income. Would I buy another tempstar? No!!!