Help! My Air Conditioner Keeps Running When Turned Off: A NJ Tech Explains | Air Experts

Before you assume there’s an issue and call a professional, check the weather. If it’s extremely hot outside, your AC may be running longer or more often than usual to compensate for the temperature outside. This is completely normal. 

However, if your AC is running continuously and never turning off, this isn’t normal and you likely have a problem with your air conditioner. 

Reasons your AC fan may be running continuously include:

  • The fan is set to ON instead of AUTO
  • Thermostat is broken 
  • The outside temperature is high
  • A relay switch is broken
  • Short circuit

Below, we’ll walk through each of these issues to help you diagnose why your AC is running when turned off. 

Reason #1: Fan is set to ON

The fan in your AC system can run separately from the cooling component of your AC. These two parts work together to cool your home, but don’t always turn on and off at the same time.

When your fan is set to AUTO on your thermostat, it will only run when the cooling component of your AC is running (when your AC system has conditioned air to blow throughout your home).

However, if your fan is set to ON instead of AUTO, it will continuously blow, regardless of whether the cooling component of your AC is on or not. 

To see if this is your issue, check your thermostat and ensure that it’s set to AUTO instead of ON. 

If your thermostat FAN is set to AUTO but your system is still running when “turned off,” you are likely experiencing one of the below issues.  

Reason #2: A broken/malfunctioning thermostat

If the temperature in your home is lower than the one you’ve set on your thermostat, your thermostat is likely malfunctioning or broken.

When your thermostat isn’t working properly, it may not be able to accurately gauge the temperature of the room, which can cause your AC to run constantly or to turn on when it should be off.

If this is your issue, you’ll need to contact an HVAC technician to check out your thermostat and repair or replace it.  

Reason #3: Outside temperature is high

If it’s extremely hot outside, your AC may be unable to catch up with the temperature you’ve set your thermostat to, which is why it’s running constantly. 

To see if this is your issue, turn your thermostat up 5-10 degrees and see if your AC shuts off. If so, this is likely the problem and is due to the fact that your AC system is too small for your home. An undersized AC system will struggle to cool your home when temperatures are high, resulting in a system that runs continuously.

Unfortunately, if this is your issue, you’ll need to contact an HVAC tech to come to check it out. If your AC system is too small for your home, you may need to consider replacing it. 

Reason #4: Stuck or damaged relay switch

Relays open and close electrical circuits to various parts of your AC system, most notably, the fan. 

Over time, relay switches can become stuck or damaged, preventing the thermostat from communicating with the fan. Essentially, this means that the fan isn’t receiving the commands you’re relaying to the thermostat. So even if you turn your AC off, the fan will continue to run. 

This is a fix an experienced technician will need to make. If you suspect you have a stuck or damaged relay switch, we would advise you reach out to your local HVAC company.  

Reason #5: Short circuit 

If your AC system short circuits, the commands you enter at your thermostat likely aren’t getting passed onto your system. So, if you turn your AC “off” at your thermostat, that command isn’t registering with the fan or cooling system, causing your AC to stay on when you’ve told it to shut off. 

As with many of the fixes above, if your system is short-circuiting, you’ll want to contact an HVAC tech to fix it. 

Need your AC fixed? Hire NJ’s Best: Air Experts 

If you’ve read through the above issues and realize you need an AC repair, we’re here to help you out. With 25 years of experience helping New Jersey homeowners with AC repairs, we’re the team you can (and should) rely on if your AC isn’t running properly. 

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