I know this has probably been discussed a lot. I've searched and cannot
find anything that specifically addresses my problem.

I recently bought a home in Western Kentucky. The house has a heat pump.
When the temperature reaches low 40's and below, the alt button lights up.
From what I understand, this is normal and indicates the heat strip is
coming on in conjunction with the heat pump in order to keep up with the
heating needs. Yesterday, the registers started blowing out nothing but
cold air. Even with the thermostat turned up to high 80s, the temperature
in the house is 67 degrees maximum. I turned it to emergency heat, which I
believe means that the heat strip is being used without the assistance of
the heat pump. Still no warm air. I have called a repair center and they
will be here sometime next week. We have a gas log fireplace in the
meantime which keeps the house fairly warm, so at least I am not freezing in
the meantime.

Since the house is only 4 years old, I wonder what could have caused this.
The previous owners had the filthiest filter in the cold air return that I
have ever seen. I doubt very seriously if it had been changed in the four
years that they owned the house. I change ours every month. Could this
have led to the problem? Any thoughts are very much appreciated.

Debbie