Air conditioner worked well during a hot summer season. However now that we're into winter, the heating function doesn't work properly. The internal thermostat seems to be broken. When I set the unit to a certain temperature, the unit stops blowing hot air when it's still upwards of 8 degrees BELOW what I have the unit thermostat set for.  And I check this with an external thermometer that I have in the room. Also, the unit turns on an off intermittently every 15 minutes or so, blows air (not hot) for 15 seconds, then shuts back off.  The only time I use the unit for heat is when I manually turn it on for a few minutes of hot air blast, then manually turn it back off. Very frustrating for a $400+ piece of equipment from a normally reputable brand.