Is your heating or cooling system not working properly?
This problem could be caused by a variety of issues—like a problem with your thermostat.
Here are some things you can try first to determine if the thermostat is the problem or if the problem lies elsewhere.
How to troubleshoot your home’s thermostat
Turn the thermostat up or down 5 degrees from normal setting
- During heating season: set the temperature 5 degrees higher than normal
- During cooling season: set the temperature 5 degrees lower than normal
You should hear a click when you do this. Wait a few minutes to see if your supply vents blow out air or if your return vents suck in air.
Make sure the thermostat is on the right setting
Just to make sure we’re not overlooking anything obvious, make sure that your thermostat is set on “heat” if it’s winter or “cool” if it’s summer.
If your issue is that your AC or furnace is blowing air constantly, your thermostat’s fan setting may be set to ON.
It should be set to AUTO, which means the blower will only blow air out the vents when the AC or furnace cools and heats the air respectively.
Replace the batteries (for electronic thermostats)
Most digital thermostats have batteries, and they’ll run out of juice eventually. Pop off the thermostat cover and replace the batteries to see if that helps.
Clean the thermostat (for mechanical thermostats)
If you’re using a lever to move the temperature setting, then you have a mechanical thermostat. They often malfunction when they get too dusty.
To clean the thermostat, remove the cover and dust inside with a small brush.
Check wire connections
Remove the thermostat cover and check the wires. Make sure each is firmly attached to its respective mounting screw.
Test the wires
Finally, we want to see if we can get the AC or furnace to work without the thermostat. If so, then that means there’s an issue with the thermostat.
Unfortunately, this step involves opening up the thermostat and wrapping certain wires together.
Because dealing with wires can be dangerous—and we certainly cherish your safety—we recommend calling a professional to test the thermostat.
Need help? Call an HVAC specialist
If the above DIY methods didn’t help, contact George Brazil for help.
George Brazil has been keeping Phoenix-area homes safe, comfortable and energy efficient since 1955.