What would cause a thermostat to stop working?

Author: Mr. Mackenzie Prosacco MD  |  Last update: Friday, October 10, 2025

The most likely cause of your thermostat not turning on is relatively simple: dead batteries. The solution is equally simple: try replacing the batteries to see if your thermostat powers back on. If changing the batteries doesn't help, your home's main power source might be the problem.

Why did my thermostat suddenly stop working?

No power: If the thermostat isn't working at all, there could be a power issue. Try checking the circuit breaker box or replacing the batteries. Bad wiring: The thermostat may be unresponsive if the wiring has gone bad. Remove the cover and check inside for loose, detached, or corroded wires.

How can you tell if a thermostat is bad?

A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.

How do you reset an unresponsive thermostat?

There is usually a small reset button somewhere on the thermostat. Finding this button may require that the thermostat panel be removed and pressing this button may require something like a paperclip to push. Hold the reset button down for 5 seconds and the thermostat should reset.

Who do you call if your thermostat is not working?

The Thermostat Doesn't Respond

If you spot these issues, contact an HVAC technician.

How to Troubleshoot a Thermostat | The Home Depot

What is the lifespan of a thermostat?

The Lifespan of a Thermostat

On average, most thermostats last about 10 years, depending on the model, usage, and proper maintenance. However, many people decide to replace their unit sooner to take advantage of new energy-saving technologies.

What are the symptoms of a thermostat not opening?

High temperature readings

The main symptoms of a failing thermostat are related to engine overheating. It can be easily noticed because the temperature gauge in the vehicle will probably read unusually high. This can be caused by the valves being stuck in a closed position.

Where is the thermostat reset button?

Locating the Reset Button

Remove the thermostat cover by either snapping it off or unscrewing it, depending on the model. Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it.

When thermostat stops working?

HVAC System Suddenly Quits Working

If the thermostat's display is dark, a lack of power may be the issue. Try replacing the batteries, then check for a blown fuse or tripped breaker in the electrical panel. If the thermostat is still unresponsive, make sure the breaker is shut off and remove the cover.

Does taking batteries out of a thermostat reset it?

To reset a non-programmable digital thermostat, you'll need to take the face-off and hold the reset button for five seconds. You can also try removing the batteries for five seconds. Both of these methods should result in a reset thermostat.

Can I replace my thermostat myself?

In most cases, installing a new thermostat is a relatively simple do-it-yourself project that can result in improved comfort and convenience and one that can help you save energy.

Why isn't my Honeywell thermostat working?

Troubleshooting a Programmable Honeywell Thermostat

Put in new batteries; Check the circuit breaker; Check the indoor unit to make sure all the panel doors are closed; Make sure the power is connected to the furnace or air conditioning unit by checking the switch near the indoor unit is up.

How much does it cost to replace a thermostat?

Replacing a Thermostat. You'll pay between $15 and $300 for the unit in addition to labor ($65 to $100 per hour) to replace an old thermostat with a new one. However, installing a brand-new thermostat is more involved and, therefore, more expensive.

How do I get my thermostat to turn back on?

DIY Thermostat Fixes
  1. Step 1: Change Batteries. ...
  2. Step 2: Check Circuit Breaker.
  3. Step 3: Check Thermostat Programming. ...
  4. Step 4: Ensure The Furnace Switch Is Providing Power To The HVAC System. ...
  5. Step 5: Facilitate Air Flow.

How do I know if my thermostat is broken?

Signs of Thermostat Failure
  1. The Heater or AC Unit Won't Start. Wiring can shift and come loose over time. ...
  2. Air Conditioner/Furnace Run Continuously. ...
  3. The Thermostat Is Unresponsive. ...
  4. Different Temperatures Throughout the Home. ...
  5. The Interface Won't Respond.

What does it mean when your thermostat goes blank?

The most common reasons for a blank thermostat screen are dead batteries, a power outage, a tripped circuit breaker, faulty wiring, or a failed thermostat. The screen will be completely dark and unresponsive when there is an issue with power reaching the thermostat.

How to fix an unresponsive thermostat?

4 Steps for Troubleshooting Your Thermostat
  1. Reset the Thermostat. Like any other electronic device, sometimes a digital thermostat needs a reset to get it working properly again. ...
  2. Clean Out Dust and Corrosion. ...
  3. Test the Power and Wiring. ...
  4. Adjust the Heat Anticipator.

Why would a thermostat burn out?

Another possible cause is a short circuit, which can occur when the wiring inside the thermostat becomes damaged or frayed. When wires touch each other or come into contact with metal, it can cause a short circuit and potentially lead to a thermostat burnout.

How do you know if you need a new thermostat?

If your thermostat has fresh batteries but suddenly lacks power, flashes, or isn't responsive to adjustments, it may need replacement. If resetting the thermostat doesn't resolve the problem, you may have wiring problems or faulty components causing your thermostat to not turn on.

How do you know if your thermostat needs to be reset?

Common Thermostat Issues that Require a Reset
  1. Misreading Room Temperature: If your thermostat reads the wrong temperature, it won't kick the HVAC system on at the right times. ...
  2. Failure to Turn On HVAC System: A thermostat reset reboots its system and attempts to restart normal functioning.

Do thermostats reset themselves?

If your thermostat is set to a temperature regulation mode or has an energy-saving program enabled, it might reset to conserve energy.

Why is my thermostat not setting?

Some of the most common thermostat issues include:

The thermostat is broken, not properly level, or dusty. The thermostat needs to be recalibrated. There is loose wiring causing a thermostat issue.

What causes a thermostat to fail?

Thermostats, like many other electrical appliances, will malfunction if they're allowed to get too dirty. Dirt, dust, and debris can pose problems for both electrical and mechanical components, causing your thermostat to fail. Turn off the power source and remove the thermostat's cover.

How do you test a thermostat?

Get an Indoor Thermometer

Another way to test your thermostat is to use a thermometer. Place the thermometer in the room and turn on the AC. After a few minutes, check the thermometer to see what temperature it's reading. The temperature should be lower than when you started.

Can a thermostat go bad without overheating?

One of the lesser-known issues is the polar opposite of overheating. Overcooling happens when the engine does not reach the right temperature for its normal function. In this scenario, the thermostat is stuck open and overflows the radiator with coolant, drastically reducing the engine life cycle.

Previous article
Do some toilets have more flushing power?
Next article
Do concrete retaining walls need expansion joints?