Thermostat Won’t Change Temperature: Causes, Troubleshooting & Fixes

Thermostat Won’t Change Temperature

A failing heating/cooling system can be the downfall of your house if not dealt with immediately. In today’s conditions, where the weather is often extreme and the days are frustrating without a working heating/cooling system at your home. 

So, if you’re going through something similar to the above-described situation- one of the first things you’ll want to do is check up on the thermostat. 

If you encounter a situation wherein your thermostat refuses to change settings, this is a bad sign.

In this case, it is likely that a malfunctioning thermostat is what is holding your heating/cooling system back. Thermostats are usually exposed to external conditions and are more susceptible to damage.

However, they are also responsible for your HVAC system, which makes even the slightest mistake on their part- well, a big deal. 

Luckily, these little remotes are easy to handle and fix, so you probably do not need to call home a technician to help you sort the issue out. 

Instead, using some tips as detailed below, you can self-learn what makes a thermostat go wrong, and how you can fix it.

How to recognize signs of a malfunctioning thermostat?

You might not always be able to realize your thermostat is failing because most units can give you some service even then. 

You might chalk it up to a bad day, even. However, here are some signs to keep in mind that should instantly help you identify a failing thermostat. 

The sooner you know, the sooner you can do something about it.

Programmable settings are lost

One of the first signs of a thermostat gone bad is eerily similar to the human body. Much like how you might lose all feeling and function in a broken arm, a broken thermostat loses its settings frequently. With programmable thermostats, users are used to scheduling their thermostats and leaving them for a long period of time.

If your thermostat keeps changing or losing these settings without any initiative on your part, something is wrong with your thermostat.

Changed Settings are not registered

You have another problem coming if you’re not able to control your thermostat at all. That is, if you’re changing the temperature, time, or any other setting, and receiving no signal from your thermostat, you have a problem. 

Usually, most thermostats will respond to any changed setting with a small beep, or you will hear your heating/cooling system turn on and work before you experience the outcome yourself. 

However, if you change your temperature, and none of these things are happening, your thermostat needs to be checked.

The heating or Cooling System won’t power on

Naturally, one of the most obvious signs of a failing thermostat is it doesn’t work well with your heating/cooling system. Traditionally, a thermostat functions by sending signals back to the heating/cooling system, according to which the entire system is powered on and settings are changed, etc. 

If your thermostat fails to turn on your HVAC system itself, and you hear no sign of life from your heat pump, furnace, or AC, it means that your thermostat isn’t working up to standard.

System Short Cycling

If you feel like your surroundings aren’t being heated or cooled enough, this could mean that your HVAC system has short cycled. 

Short cycling is a process by which a heating/cooling system turns off early due to faulty sensory mechanisms on part of the thermostat and leads to insufficient heating or cooling throughout your home.

Why Your Thermostat Is Not Changing Temperature?: (Cause & Fixes)

All the signs above are quite problematic in themselves. But a thermostat that doesn’t reach its set temperature may have deeper underlying problems that you might want to examine. 

Most of them have to do with a broken or incompatible thermostat, and the ideal solution sometimes could be the replacement of the thermostat entirely. 

Still, if you want to specifically tackle the issue of your thermostat not reaching the set temperature, these are some causes you can attribute to it:

Your thermostat is broken

As mentioned, the most direct, plain, and simple cause behind the problem is that your thermostat is broken. For instance, if you have a programmable thermostat that keeps shutting off unexpectedly, or displays a temperature that differs from the temperature in your surroundings, all signs point to a broken thermostat.


One of the most common ways to identify a broken thermostat is to make note of temperature disparity. You could use a thermometer to check the room temperature, and see if it matches up to the numbers displayed on your thermostat. If there’s a clear difference, it is time to cash in a replacement.

Your thermostat is too small

You might not realize it, but one of the biggest reasons for your thermostat failing to work effectively is that it is simply too small for your home and your HVAC system. 

Much like an AC, or a furnace, even a thermostat has a required surface area that it is capable of covering. If it is too small for your living space, it won’t be able to get an accurate reading, and in turn, would lead to faulty functioning of your heat system.


There’s really no way to fix a thermostat too small for your home, so the ideal solution would be to get a replacement of the correct size. To help you size the thermostat appropriate for your homes, you could call in a professional for help.

Your thermostat is frozen

If you have a smart thermostat, a likely explanation is that static electricity around the thermostat is causing the device to freeze up. This means that your thermostat fails to send the data and signals it collects back to your HVAC system. In turn, the set temperature is not reached.


In the case of a frozen thermostat, the best solution is to reboot and restart the whole device, much like a mobile phone. You can turn it off and wait for a few seconds before switching it on.

Your thermostat has lost its power

Without electricity, no powered device will be able to work. Obviously, the same is true for your thermostat as well. If you notice that your thermostat switches off abruptly and the screen goes black, this could be indicative of the fact that your thermostat is not receiving the power required to function appropriately. This stops the thermostat from reaching its set temperature.


You can check up on your heating/cooling system to see if it is receiving power as well. If not, you might want to repair your heating/cooling units.

Your thermostat’s fan is dysfunctional

Sometimes, it might not be that your thermostat is failing to respond to the set temperature, but the problem might lie in your fan and its connection with your furnace. If your fan keeps pumping out cold air even after you’ve tried to switch it off, however, it’s probably your thermostat’s fault for failing to send the right signal.

Your Thermostat Needs Cleaning

Another reason behind your thermostat’s misguided functioning might simply be that it has not been cleaned in a long time. Any accumulated dust and debris, especially close to the wiring, might be tampering with the furnace-HVAC system connection.


You can deal with this by clearing the area behind your thermostat with a small, soft brush.

Your thermostat has reached its Temperature setting limits

Most temperatures have in-built limits to how high, or how low they can set the temperature. If you are trying to set your thermostat to a temperature that is beyond either of these limits, you’re not going to get any response.


Ensure that you are thoroughly familiar with your thermostat’s details by going through the manual. This should help you gain some knowledge of your device’s temperature settings.

Your thermostat is working in Auto Mode

The auto mode on your thermostat will completely block you from making temperature changes. This is because the Auto mode has pre-set temperature ranges programmed into it, according to which it runs the heating/cooling system. At this time, the heat or cool modes are usually self-automated, and you can’t set your own temperature.


In this situation, you will have to exit the Auto mode and go back to Heat or Cool mode, and manually set your temperature.


These were some of the most common why’s and how’s behind a thermostat that fails to comply with a temperature setting. You might notice that some of these solutions apply.

You might even notice that none of the given solutions apply, in which case- your thermostat is broken and needs replacement. Also, consider if your thermostat is too old for your heating/cooling system and if you’re due for a brand new one.

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