I have a Trane heat pump.Inside unit is about 13 years old, the outside unit is about 8 years old. I think it is a 3 ton unit. Original weathertron thermostat.
During a recent cold snap (outside temp about 15), we noticed the house temp wouldn't get above 65 F. The blue aux heat light was on but I don't think the heater strips ever energized. To test, I measured the air temp at a vent before and after the blue light came on. No difference. Then I tried switching to emergency heat. This cut out the compressor (as expected) and the vent temperature started to drop. So, I think the the emergency heat is also not working.
I checked all the breakers. What do the emergency heat strips and the aux heat strips have in common? I'm thinking that they share a common ground that may be bad? Any other ideas?
Thanks
Mitch