I have an electric heat pump with electric coil emergency heat. The unit (Armstrong) was serviced about a month ago and checked out OK.

The past week or so, I hear the fan running constantly, and every time I look at the thermostat, the unit is in Emergency mode. I have not been able to adjust the thermostat w/o it eventually clicking into Emergency.

Concerned about the amount of electricity I have just wasted, I changed out the thermostat. Everything tests fine at first, but I am noticing that with the heat on, it starts warm and gets cold. The outside compressor kicks on and the outdoor fan runs. The thermostat makes the necessary 'clicks' and appears to be working properly. The fluid in the insulated line, between the house and the outside unit, starts getting warm, then gets cold. After a period of 30min, the house actually starts getting colder.

I do not hear fluid rushing through the lines like I used to. It has been very cold outside over the past 2 weeks, but has been warm yesterday and today.

The cooling function seems to work well - at least it starts getting pretty cold. I have not had the cooling section on for very long though.

It is in the 60's outside today. The thermostat says 67F inside. I set the heat to 69F and it never goes above 67, but actually drops to 66.

There are no signs of obvious damage or ice outside.

Could it be a stuck reversing valve? Is there anything a homeowner can do to diagnose or fix this?

Thanks for your help.