My AC unit worked quite well throughout the summer season. There was a brief reprieve wherein neither AC nor Heat were required so I set my digital thermostat to OFF. When it became chilly, I switched it to Auto Heat. Nothing happened. I waited and even adjusted the desired temperature up in an attempt to force the heat to come on, still nothing. I checked the circuit breaker to ensure it hadn't tripped and all breakers are in their proper place. I decided to see if the AC would come on; adjusted the temperature to make that happen... and again... nothing. I switched the fan from Auto to On and nothing there either. I have replaced the batteries in the thermostat, in case that was the problem... but, well, I'm sure you guessed it... nothing. Is this an HVAC or electrical issue? Any helpful feedback will be appreciated.

Oh... I'm not sure how old the heating unit/furnace (whatever the proper name) is, but I believe it is a Carrier brand and is Gas. It is at least 6 years old because that's how long I've been in this house. The AC unit is approximately 4 years old having been replaced a couple of years after I moved in.

Have you checked breakers? Is the door on furnace good and tight?

Make sure that you filter door in in the right place and secure because if the door switch is not pushed in nothing will work... If you need more help let me know.

Do you know if the thermostat powers offthe furnace and the batteries are for back up? Breakers can be tricky. Sometimes you need to turn it all the way to off and back on. Most furnaces have an power on LED. Is your on? If not, check the control voltage fuse. How? See the sticky at https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html