9 Signs Of A Bad Thermostat

When we buy a new thermostat we tend to think that it may last forever, but they do not. In this post, I am going to share with you 9 signs of a bad thermostat so that you can tell if it is time to replace it.

9 Signs Of A Bad Thermostat

9 Signs Of A Bad Thermostat

1: The thermostat does not turn on

This is the first sign that you have a bad thermostat, it does not turn on, you changed the battery ( for battery-powered thermostat), or verified electrical connection, the display does not appear, it is a clear sign of a bad thermostat.

2:The thermostat is unresponsive to your adjustments

You feel like the house is too hot or too cold and you want to change the temperature setting but the thermostat is not responding or the display does not change when you press the buttons.

3:The AC or furnace won’t come on

On point number 2 above we mentioned that sometimes the thermostat will stop responding to your adjustment, if the display responds but the cooling or heating system (HVAC) does not come on, could mean that the thermostat is bad, most of the time this is due to a wiring problem.

If you make changes at the thermostat and nothing happens, that’s another sign you have a bad thermostat.

4: The room temperature doesn’t match the thermostat setting

One of the reasons that the room temperature is not as your thermostat setting is that the thermostat is coming on and off when it is not supposed to. 

If the thermostat is resetting itself without your inputs or just cycling it could cause some rooms to have different temperatures than your settings.

5: The programmed settings reset themselves

This happens a lot with programmable thermostats, when you figure out that each time you program your thermostat and it reset by itself, it could mean that the thermostat can not retain the memory, and this is due to internal electronic system failure, most of the cases there is no fix for this, you will need to replace the thermostat.

6: The HVAC system won’t stop running

Most thermostats will come with a button where you can set your HVAC on or off, if you try to turn it off and it does not stop running this is another indication that your thermostat might be bad.

7: Thermostat buttons aren’t working

If you have a thermostat with buttons for programming and they are not working when you are pushing them, it could mean the buttons have loose wires.


The buttons are mechanical, so they have wires that help them to retain their position after being pushed, if these wires become loose they will stop responding, most of the time it is not worth trying to fix them if this is your case I will recommend replacing the thermostat.

8: You receive a high energy bill

Let’s talk about money if suddenly you see an increase in your electric bill, it could be that the thermostat is losing its efficiency and it needs to use a lot of energy in order to maintain your house at a desirable temperature. This happens a lot with older thermostats.

9) You have an old thermostat

As I mentioned in point number 8, when thermostats get older they start to lose efficiency and they will start misbehaving.

Typically, thermostats have a life expectancy of  10 years or longer. After the decade passes, your thermostat may start to malfunction.

Check the model of the thermostat to see how old it is before you make the diagnosis that it’s just outdated so “it must not be working properly”.

How to diagnose if your thermostat is bad

Now you know the 9 signs of a bad thermostat, let’s say you find a few of them on your thermostat but you are not sure here is the step-by-step guide that shows you how to tell if your home thermostat is bad with some simple tests.

Step 1: Make sure the thermostat is ON

This might sound very basic but it happens many times, buttons are mistakenly pushed all the time. Make sure the thermostat is on and double-check that your HEAT or COOL setting is selected.

Step 2: Check the power

All electronic devices need the power to run, so what you need to do is to check if the batteries are not depleted in case your thermostat is powered by batteries, try new and fresh batteries.

If it is connected to the house electricity just make sure that the electricity is reaching your thermostat, if you have an electricity test use it also make sure the switch on the circuit breaker is switched on.

Step 3: Reset the thermostat lower or higher

If there is power and your thermostat is on, the next step is to check and see if the heat or AC turns on if you set the thermostat 5 degrees higher or lower than normal.

Observe if you see any changes in your heating or cooling system, if nothing is moving then go to the next step.

Step 4: Check the wiring

If in step three above nothing is changing, it could be due to bad wiring, if your thermostat is running on the electricity turn the thermostat’s breaker off. Open the thermostat cover and make sure all wiring is properly attached and screws are tight.

Step 5: Turn the power  back on

In step 4 you turned the power off to check the wiring. Turn it on again and observe if the thermostat turns on and functions properly after turning the breaker back on. If the thermostat doesn’t turn on or appears faulty, retest by turning the breaker on and off again.

Step 6: Wrap wires together

Turn off the power again, remove either the AC wires or furnace wires from their port and wrap them around each other.

Turn the breaker back on. If the AC or heat turns on, it’s likely that your thermostat is what’s causing the problem.

If nothing works you could be having a bad thermostat and you will need to upgrade it, my recommendation would be to peak a smart thermostat that will need no programming and help you to save energy.

nest learning thermostat


That is it, those are 9 signs of a bad thermostat, if you see any of those signs present on your device please use our diagnostic guide steps to figure out what is the issue.

If you can not find out what is the problem either call an HVAC technician or replace the thermostat, whichever comes cheaper.

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