Troubleshooting Thermostat Controls
Your thermostat is the “boss” of your heating and cooling system if it stops working, your whole HVAC system can act up.
Here are the most common thermostat issues and what you can safely check.
Common Thermostat Problems
You may notice one or more of these:
Thermostat screen is blank
Heating or cooling won’t turn on
Room temperature doesn’t match what the thermostat shows
System turns on/off too frequently
System runs nonstop
Buttons don’t work, or you can’t change the temperature
These issues are often simple to fix.
1. Thermostat Screen Is Blank
Try this first:
Replace the batteries (most thermostats use AA or AAA)
Check your home’s breaker panel for a tripped breaker
Make sure the thermostat’s faceplate is fully clicked in
For wired thermostats, check if the furnace power switch is ON
If the screen stays blank after all this, the thermostat may be faulty.
2. Heating or Cooling Won’t Turn On
Before assuming the furnace or AC is broken:
Make sure the thermostat is set to Heat or Cool
Set the temperature at least 5 degrees above or below the current room temperature
Check the furnace/air handler switch (looks like a light switch near the unit)
Check for a tripped breaker
If nothing starts running, the issue may be with the HVAC system, not the thermostat.
3. Room Feels Too Hot or Too Cold
If the thermostat doesn’t match the actual temperature:
Make sure the thermostat isn’t in direct sunlight
Keep lamps or electronics away from it (they give off heat)
Replace or clean your HVAC air filter
Dust around the thermostat to ensure proper sensing
Large temperature swings could also indicate a furnace or AC issue.
4. System Turns On and Off Quickly (Short Cycling)
Short cycling can be caused by:
Dirty air filter
Wrong thermostat settings
Thermostat wiring issues
Incorrect thermostat placement
Furnace or AC safety shutdowns
Try replacing the filter and restarting the thermostat.
If the problem continues, contact a professional.
5. System Won’t Stop Running
Check for:
Thermostat set to Fan: ON instead of AUTO
A stuck relay in the furnace or air handler
Temperature set too high/low
Very dirty filters causing airflow problems
If the system runs nonstop even on AUTO, the issue is likely in the HVAC equipment.
6. You Can’t Change the Temperature
This often means the thermostat is locked.
Try:
Pressing and holding the up + down buttons together for 3–5 seconds
Checking the menu for “Lock” or “Screen Lock”
Replacing the batteries
Smart thermostats may require unlocking through an app.
When You Should Replace Your Thermostat
Consider upgrading if your thermostat:
Is more than 10–15 years old
Shows the wrong temperature
Has a slow or frozen display
Keeps losing schedules
Makes your energy bill unusually high
Randomly resets or shuts off
Has broken buttons or unresponsive touch controls
Modern thermostats improve comfort, energy efficiency, and reliability.
When to Call a Professional
Contact an HVAC technician if:
The thermostat stays blank after new batteries
Your system doesn’t respond to thermostat changes
The furnace or AC cycles rapidly
You smell burning, gas, or notice unusual behavior
You tried all steps and nothing improved
A professional can diagnose whether the problem is the thermostat or the furnace/AC.