7 Ways to Tell If a Thermostat is Bad

Alison Kasch
Written by Alison Kasch
Updated January 13, 2022
A woman adjusting her house’s temperature using her mobile phone
Photo: SDI Productions / iStock / Getty Images

These symptoms can indicate a faulty thermostat—or issues with your HVAC system

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If there seems to be a major discrepancy between your HVAC system and the number on the thermostat, there may be an issue at hand. Rather than putting on an extra sweater and giving it the side-eye, you can diagnose a problem by spotting these telltale signs.

1. Your Thermostat’s Batteries Are Fine—But It Still Won’t Work

Your thermostat’s batteries are an important thing to check before calling for HVAC service. While this might seem like a no-brainer, it’s an easy thing to overlook while you’re checking for other symptoms of a bad thermostat. If you haven’t already done so, try replacing the thermostat’s batteries with fresh ones before you continue your troubleshooting.

2. The Thermostat Doesn’t Turn On or Is Unresponsive

If you’re looking at a blank screen despite a brand-new set of batteries, or if you’re seeing a flashing screen that won’t respond when you hit a button, there’s an issue. Call a local thermostat repair contractor to come and have a look.

3. Your Home’s Temperature Doesn’t Match the Thermostat

If your A/C is set to 66 degree Fahrenheit and you’re still getting stuck to your leather sofa, there may be a thermostat problem. However, there could also be an issue with your HVAC system as a whole. A local A/C repair contractor or heating repair service near you can get to the bottom of whatever’s going on.

Note: If your thermostat is set to “auto” versus “on”, you should only feel airflow while the system is running. If you find that your home is too hot or too cold, try using the “on” setting and see if it makes a difference.

4. The Thermostat Won’t Maintain Programmed Settings

A woman setting the temperature of the room by using the thermostat
Photo: Westend61 / Getty Images

When you’re relying on your thermostat to maintain a constant temperature while you’re on vacation or just at home watching Netflix, it’s incredibly frustrating when it won’t cooperate. Before Dad gets upset about someone touching the thermostat, know that losing programmed settings is a major sign that a thermostat is bad. If the temperature reads 65 degree Fahrenheit when you just set it to 71 degree Fahrenheit, it might be time to budget for the cost to install a new thermostat.

5. Your HVAC System Won’t Respond to the Thermostat

Your HVAC system should respond right away when you change the temperature on the thermostat. You’ll usually hear a couple of clicks, followed by the system kicking on. 

Getting radio silence no matter what you change the settings to? First, check your circuit breakers to ensure that your HVAC’s circuit didn’t get tripped. If all is well with the breaker box, it might be time to replace the thermostat or even invest in the cost of a new HVAC system.

6. You Have a Short-Cycling A/C or Furnace

When your HVAC system short cycles, it stops too early and won’t complete a full heating or cooling cycle. Again, this could be an issue with the thermostat, but it could also be a problem with your entire HVAC system. Call in a pro to come and have a look.

7. Your Thermostat Is Old and Outdated

If your thermostat looks like a relic from the ‘90s and can’t seem to do its job properly, it’s better to upgrade rather than repair. You can choose a smart thermostat, which offers high-tech capabilities to maximize your system’s energy efficiency. They’re not for everyone, though, so there are a few questions to ask before considering a smart thermostat

For those who’d rather have something more basic, there are plenty of great options as well. A thermostat installation contractor near you can help you pick what’s best for your home.

How Do I Test My Home Thermostat?

Before you pay for an HVAC service call, it’s wise to troubleshoot your thermostat. Here’s how to do it:

  • Ensure your thermostat has working batteries

  • Double-check your settings and make sure the system is set to “heat” or “cool”

  • Change the temperature settings and see if the HVAC system kicks on

  • Try changing the fan to “on” instead of “auto”

  • Check your breaker box to make sure your HVAC’s circuit is intact

  • Remove the thermostat’s cover and ensure that all wires are properly connected

If everything seems to be in working order, pass this one off to the pros. An HVAC repair technician can diagnose the problem and get your system up and running again in no time.

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