AC Thermostat Not Working

Beth Huston Profile image

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Updated May 17, 2023

The best air conditioners are only helpful when they’re fully functional. So, if you’re asking yourself, “Why is my air conditioner thermostat not working?” you’re in the right place. Perhaps you’re noticing certain signs, such as your bad thermostat screen showing a certain temperature that’s vastly different than the actual temperature in your home. A malfunctioning thermostat and temperature discrepancies can be a frustrating problem caused by a dirty filter, blown fuses, or dead batteries, so keep reading, and we’ll delve into the issues that could be causing it below.


  • Modern thermostats can be finicky and may need troubleshooting, even if they’re so much better than the options that we used to have.
  • Several reasons your thermostat may not work include a blown fuse, a tripped circuit breaker, and dead batteries.
  • You may also have a broken thermostat, which might be cheaper to replace rather than get fixed.

Why Your AC Thermostat Isn’t Working

As with any appliance, there are a few things that could go wrong with your air conditioning unit. If the wiring isn’t done correctly, the thermostat installation could be faulty, and your indoor temperature will suffer as a result. As another example, some people might find that their air conditioner is running when the heat is on. If your unit is locked so the kids can’t mess with the temperature, check out our page on unlocking an AC thermostat if you forgot how.

Insider Tip

If you get a programmable thermostat, you’ll be able to have preset thermostat settings.

You can troubleshoot and fix most of these problems easily. Check and adjust the temperature settings to make sure that they are in the right range. Cleaning filters that are clogged with a buildup of dirt is key, as this can cause issues with performance and energy efficiency. Plus, it’s a good idea to replace filters when necessary.

However, in some cases, you might need to hire a repair service, and in the worst of situations, you may even have to replace your air conditioning system.

If your AC is indeed damaged beyond repair, you might ask yourself, “Do I need a permit to replace an air conditioner?” While unlikely, it is possible. Frankly, a complete replacement is a big job, so if you’re inexperienced, call a professional technician for help. However, learning how to set the thermostat shouldn’t require a professional, although you may need to check the manual.

You Need to Check Your Circuit Breaker

One reason for thermostat issues is that you may have accidentally tripped the circuit breaker. If this happens, all you have to do is go and check the breaker box to see if it has been tripped. Once you reset it, see if the problem is fixed.

Your AC Unit Has a Blown Fuse

Most homes no longer have electrical fuse boxes, as these were replaced with circuit breakers panels starting in the 1960s. However, your AC unit may have internal fuses. This electrical issue can be a real pain, especially since multiple fuses could be the issue. If you suspect this is the problem, it’s best to call an air conditioning technician to fix it.

The Batteries Are Dead

Not all AC thermostats are hardwired. A common cause of problems for any electronic thermostat that runs off battery power would be bad batteries. If you have a battery-powered unit, check the thermostat batteries to see if that’s the problem. If they’ve run out of juice, just replace them.

STAT: Total shipment for air conditioners fluctuate year to year, generally falling between 3.5 and 6 million. (source)

You Have Dirty Air Filters

A dirty air filter is one of the most common air conditioner issues out there, and it can affect your unit’s thermostat. Dust and dirt can accumulate over time without regular cleaning or replacing, leading to a faulty thermostat and poor performance. This might also be why your central ac is not blowing cold air. If you’re cleaning or replacing your AC filters regularly, you shouldn’t have to worry too much about this issue. However, if you think it’s the filter, either replace it with a new one or clean it (if it’s reusable).


What are programmable thermostats?

If you have a programmable AC model, you can adjust settings and temperature using a smart system. This allows you to choose from preset modes.

Should I hire an HVAC professional?

While a costly repair might make you go blue in the face, it’s always better to have things assessed by a professional. This takes out a lot of guesswork and gives you a better understanding of the problem.

What are digital thermostats?

A digital thermostat is a modern amenity that you can often purchase to install in your home. This will allow you to set the temperature quickly, see the current temperature inside, and even see the temperature outside.

Is an indoor unit better than an outdoor unit?

There are pros and cons to both styles, so you should weigh them carefully before deciding which type of unit to purchase.

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