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

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

Do you know why your programmable thermostat won't reach the desired temperature? You are not alone, though. Numerous homeowners are also battling the issue. It can be highly frustrating when the room temperature displayed on the thermostat screen is below or above the temperature you set because it is so bitterly cold or hot outside. So what do you do when the thermostat setting and the room temperature are different? In this article, we'll examine the best fixes for this problem and the most typical causes of it.

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 where your thermostat refuses to change settings, this is a bad sign.

In this case, a malfunctioning thermostat is likely 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 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 to fix it.

Signs of a Malfunctioning Thermostat - Thermostat Won’t Change Temperature

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 if you cannot 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 Will Not Power On

Naturally, one of the most apparent signs of a failing thermostat is it doesn’t work well with your heating/cooling system. Traditionally, a thermostat sends 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 the part of the thermostat and leads to insufficient heating or cooling throughout your home.

Thermostat Malfunctioning Causes & Fixes - Thermostat Won’t Change Temperature

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 note temperature disparity. You could use a thermometer to check the room temperature and see if it matches 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 can cover. If it is too small for your living space, it won’t be able to get an accurate reading, leading 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 home, you could call in a licensed contractor 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 indicate that your thermostat is not receiving the power required to function appropriately. This stops the thermostat from reaching its set temperature.

You can check your heating/cooling system to see if it also receives power. 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, it’s probably your thermostat's fault for failing to send the right signal.

You can check the wiring on your thermostat to ensure that it is correct.

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 tamper 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 beyond either of these limits, you will not get any response.

By going through the manual, ensure you are thoroughly familiar with your thermostat’s details. 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. The heat or cool modes are usually self-automated at this time, 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.

Conclusion - Thermostat Won’t Change 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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How to Fix Thermostat Read Temperature

It's always a good idea to speak with an HVAC expert before taking the DIY route. If you live in the Baltimore metropolitan area and require a thermostat replacement or a quicker and more effective repair, SuperTech has you covered. And to avoid your thermostat not reaching the desired temperature when you move into a new home, be sure to get an HVAC inspection before you move in.

What should I do when the thermostat doesn't reach the desired temperature?

If the temperature in your house or place of business is not what you prefer, your thermostat may be broken. Your thermostat might occasionally have technical issues, just like any other device. It won't accurately assess the temperatures or provide the readings if the program it uses crashes. This manual may be helpful if you want to find out how to check the programming on your thermostat.

Another option is to buy a thermometer designed for air conditioning and use it near the thermostat to compare the variations in the two readings. After that, calibrate the thermostat using the thermometer readings and its user manual.

Rewire the thermostat

The wiring may be the issue if you recently purchased a new thermostat, which has been problematic since installation. After a do-it-yourself installation, this mostly occurs. To reconnect all wires to the proper terminals, refer to your manual.

Other times, lint and corrosion may accumulate on the wiring and obstruct the flow of current. If you feel uncomfortable handling wires, an HVAC technician can examine your thermostat problem and resolve it.

A buildup of dirt in the thermostat's internal components may cause temperature differences between the room and the thermostat setting.

A layer of dirt around the inner parts could generate too much heat and lead to inaccurate readings from the thermostat. Remove the faceplate from the thermostat and use a clean, soft brush to scrub away any dirt gently. During yearly

You won't have to worry about this problem because a professional will check and clean your thermostat's wiring as part of a furnace or air conditioner tune-up!

Maintain Levelness in Your Old-Model Mechanical Thermostat Old round-dial thermostats can malfunction if certain internal parts aren't level. A mechanical thermostat, as opposed to a typical digital one, regulates temperature using bimetal springs and a horizontal mercury switch. Therefore, the accuracy is affected if the switch tilts.

Remove the thermostat's faceplate, look for the glass mercury tube, and balance it with a tiny level to fix the broken thermostat. Even better, you can replace the outdated, defective thermostat with a more advanced, efficient thermostat.

If the thermostat is frozen, restart it.

Your thermostat may freeze and fail to show any data updates if there is a problem with the static electricity in the area.

It can be challenging to notice that your electronic thermostat isn't setting the proper temperature in this scenario. The best course of action is to turn off the device, wait at least ten seconds, and then turn it back on.

Switch Out Your Old Thermostat

Don't be shocked if the room temperature differs from the thermostat setting or your device is too old.

A malfunctioning old thermostat could give the furnace, air conditioner, or heat pump incorrect temperature readings for your house. Furthermore, the heating and cooling system cannot deliver the precise temperatures you require without accurate information. So, think about upgrading your thermostat.

Install a Different Thermostat

The extra warmth in these areas may deceive the temperature sensor into thinking there is more warm air in the house than there actually is if your thermostat is placed close to a window that receives a lot of direct sunlight, the fireplace, or the kitchen. This indicates that your thermostat is unable to detect the temperature inside accurately.

If so, relocate it with the help of a certified HVAC specialist. The expert will assist you in locating the ideal relocation location.

Alternative Remedies If The Thermostat Doesn't Reach The Set Temperature

Sort out any problems with the HVAC system that might affect the temperatures.

You can follow the steps listed below.

  1. Clean your air ducts, filters, and vents. Since the dirt and debris accumulation prevents air from flowing through the vents, an obstructed air filter will struggle to maintain the temperature set by the thermostat. Additionally, comfort levels decrease as airflow into living areas decreases. Thankfully, maintaining your filter, vents, and ductwork will help to improve circulation and make it easier for your HVAC system to maintain thermostat settings. Replace or clean your air filters first. Wash the vents thoroughly, and clean the ductwork in cooperation with a qualified HVAC specialist. Additionally, they'll search for duct system leaks that allow heated air to escape.

  2. Size Your HVAC Unit Correctly - When installing your new heating or cooling system, did a seasoned HVAC contractor inspect your home? You might be looking at an AC unit or furnace that is too big or small for your home if the installation company didn't follow the correct HVAC system sizing procedure. The wrong unit won't provide the same comfort levels as an appropriately sized one. To determine the best action in this situation, speak with a qualified professional.

  3. Investigate Alternative Strategies When Outdoor Temperature Is Record-Breaking. The thermostat might fail to reach the desired temperature if the outside weather is extreme. Sometimes, even with its maximum capacity, your HVAC system simply cannot keep up with the extreme outdoor temperatures. Use alternative strategies in this case, like drawing the drapes and closing windows, caulking any leaks around your home, and running a ceiling fan if it's hot outside.