Hello. I have a relatively new house (2.5 years) that has an American Standard Heat Pump (2a6b3018-060a1000a). It also has some form of American Standard aux heater (bayhtr?? ) in the air handler. This is controlled by a Panasonic TH8000 thermostat.

We have had a long period of cold weather here in Seattle and I have noticed that during this time two unusual behaviors are happening with my heating system:

(a) I have not see the AUX Heat indicator come on on the TH8000 thermostat. I have seen this frequently before and I took it to mean that the aux heater was helping the heat pump along. But I have not seen it at all in at least a week and I have looked frequently at the thermostat.

(b) There are times when the heat pump is not operating (I can see the fan blades stopped) but there is significant cool air (not icy cold but certainly not warm) coming out of my heating ducts. It is clearly being blown by a circulating fan in the system but there is no warmth.

I have looked as much as I can at the heating unit under the house and see nothing unusual. I checked the electronic air filter and it seems fine.

Any idea what may be wrong here? Thanks.