Thermostat Not Working? Here’s What to Check First
If your thermostat isn't turning on, isn't responding, or isn't controlling your heating or cooling system properly, there are several safe things you can check before scheduling a repair. Follow the steps below to help determine whether the problem is with the thermostat or your HVAC system.
Common Reasons Your Thermostat Isn’t Working
A thermostat can stop working or fail to control your HVAC system for several reasons. Start with these common problems before assuming the thermostat or heating and cooling equipment needs to be replaced.
1.
Check Your Thermostat Settings
Make sure your thermostat is set to the correct mode for what you need. Select Cool for air conditioning or Heat for heating, and set the temperature several degrees beyond the current room temperature. If the thermostat has a fan setting, use Auto instead of On while troubleshooting.
What to look for: After changing the temperature, give the system a few minutes to respond. Listen for the heating or cooling system to start. If nothing happens, continue with the next checks.
2.
Check the Thermostat Display and Batteries
If the thermostat screen is blank or not responding, check whether it uses replaceable batteries. If it does, replace them with fresh batteries and make sure they are installed in the correct direction. Some thermostats receive power directly from the HVAC system and may not use batteries.
What to look for: If the display turns back on after replacing the batteries, give the thermostat a few minutes and see whether the heating or cooling system responds. If the screen remains blank or the thermostat still doesn't respond, continue to the next check.
3.
Check Your HVAC Breakers
If the thermostat is blank or the heating or cooling system isn't responding, check your home's electrical panel for a tripped breaker. Your HVAC system may have separate breakers for the indoor equipment and the outdoor unit.
What to look for: If you find a tripped breaker, reset it once. If the breaker trips again, stop troubleshooting and contact an HVAC professional. Do not repeatedly reset a breaker that continues to trip.
4.
Check the HVAC Power Switch
Many heating and cooling systems have a power switch located near the indoor equipment that looks similar to a regular light switch. Make sure this switch hasn't accidentally been turned off.
What to look for: If the switch was off, turn it back on and give the system a few minutes to respond. Check whether the thermostat display returns or the heating or cooling system begins operating. If the switch was already on, continue to the next check.
5.
Check the Air Filter and Airflow
A dirty air filter can restrict airflow and may cause some HVAC systems to shut down or stop heating or cooling properly. Check the filter and replace it if it is heavily covered with dust or debris. Also make sure the supply vents and return-air grilles aren't blocked.
What to look for: After replacing a dirty filter, give the system several minutes to respond to the thermostat. If the thermostat is calling for heating or cooling but the system still doesn't operate normally, continue to the next check.
6.
Check Whether the Thermostat Is Calling for Heating or Cooling
Set the thermostat several degrees above the room temperature for heating or several degrees below it for cooling. Look at the thermostat display for a message or symbol showing that the system is trying to heat or cool the home.
What to look for: If the thermostat indicates that heating or cooling should be running but the HVAC system does not start, the problem may be with the equipment rather than the thermostat itself. Avoid removing thermostat wires, equipment panels, or bypassing any controls to test the system.
When to Stop Thermostat Troubleshooting and Get HVAC Help
Some thermostat and HVAC problems should not be handled as a homeowner troubleshooting project. Stop troubleshooting if a breaker repeatedly trips, you notice damaged or exposed wiring, smell burning odors, or diagnosing the problem would require removing equipment panels, handling thermostat wiring, or working around electrical components.
If the basic checks above didn't identify the problem, FixWithAPro can help you take the next step. During a live video session, an experienced HVAC technician can review what your thermostat and system are doing, guide you through additional safe checks, and help determine whether the problem is with the thermostat or requires an in-person HVAC professional.
Thermostat Not Working FAQs
Why is my thermostat not working?
A thermostat may stop working because of dead batteries, incorrect settings, loss of power to the HVAC system, a tripped breaker, or a problem with the heating or cooling equipment.
Why is my thermostat screen blank?
A blank thermostat screen may be caused by dead batteries or a loss of power to the HVAC system. Check whether your thermostat uses replaceable batteries and verify that the HVAC breakers and nearby equipment power switch are on.
Why does my thermostat say heat or cool but nothing happens?
If the thermostat indicates that heating or cooling should be running but the system doesn't start, the thermostat may be sending a call while the HVAC equipment is unable to operate normally. Further troubleshooting may be needed to determine whether the problem is with the thermostat or the equipment.
When should I call an HVAC professional for a thermostat problem?
Get professional help if the basic checks don't solve the problem, a breaker repeatedly trips, you notice damaged wiring or burning odors, or diagnosing the problem would require handling thermostat wiring or opening HVAC equipment panels.