Heil 1300 DX was installed 12/01/2007. Everything seemed fine. Last night (5 days after installation) I happened to walk by the outside unit just as it seemed to be going into defrost. Problem is it never removed the frost from the unit. This continued for about 5 hours. I called the installer and he said he would check it today (12/07/2007). I asked if I should shut it down and he said it would be OK to leave it alone. First of all the fan was running quite a bit slower than in "normal" mode and there were some smells coming from the
outside unit I wasn't comfortable with, so I turned it off at the thermostat and switched to emergency heat for the night. Luckily, here in Alabama the high today is about 60. Last night it might have been 35, if any of this matters.

My question is, what would cause the unit to go into defrost mode but not remove the frost?

Thanks for reading.