My air conditioner keeps turning off and on by itself. Help!

In the past, I have had some of my clients wondering why their air conditioner keeps turning on and off by itself.

For this reason, today, I will be guiding you on what might be causing your air conditioner to frequently turn on and off by itself.

In addition to that, I will show you what you can do to fix it.

My air conditioner keeps turning off and on by itself – what it means and what you can do

Before I tell you what you can do about it, let me first tell you why your AC keeps turning itself on and off.

Why does my air conditioner turn on by itself?

For the most part, it is perfectly normal for your AC to turn on and off by itself (even though it might seem puzzling at first).

Here’s why…

ACs are designed to continuously toggle on and off once they reach a specific temperature.

By doing so, the unit is able to be energy efficient while maintaining a comfortable (and cool) environment.

So, don’t be alarmed if your AC is turning on and off by itself – it’s simply functioning as it should.

Pro tip: Typically, the average time an AC should stay on between cycles is around 10 minutes. This is after running a cycle of 15 to 20 minutes.

However, if your air conditioner is frequently turning on and off, it could be an indication that something is up.

Subsequently, you ought to inspect the unit.

This is more so if the AC is short cycling more often than it used to – within a few seconds or minutes.

With that in mind, below is what causes this and what you can do about it…

Air conditioner runs for a few minutes then shuts off – what might be causing it and what you can do

To start with…

Turn off smart mode and adjust the thermostat settings

why does my air conditioner turn off by itself

By default, ACs have the cool differential set to 0.5⁰F.

However, this is quite low and will often result in your AC turning on and off frequently – within minutes.

Now, to fix this, first deactivate your AC’s smart mode.

Next, set the cool differential to 1⁰F – you can also set it a bit higher depending on how much heat you can tolerate.

Something else: You can also increase the min (minimum) cycle time and the compressor’s min on time.

By doing so, you’ll be reducing the number of times the AC turns on and off to suit your preference.

Clean the coils and filters

Dirty coils and filters will result in your compressor overworking and thereby overheating it.

In turn, this will turn it off (it will resume shortly after it has cooled) – and the process will repeat.

So, be sure to clean the filters and coils.

Pro tip: Clean the filters every 2 weeks or so.

Clean the drain line

You see, a clogged drain line will kick in the float switch.

Once the unit has drained a little bit, the float switch will deactivate within minutes (or seconds) only for it to be reactivated almost immediately.

And the process will repeat itself.

With that in mind, make sure to clean the drain line (and remove any clogs that might be in there).

Confirm that you are using the right AC for your room size

In the past, I have had clients who purchased ACs meant for large rooms and installed them in smaller rooms.

This means that the AC will quickly cool the room and turn off only to turn on after a few minutes especially if the cool differential is quite low.

Bearing that in mind, you can quickly estimate the AC you need by multiplying your house’s area (in sq. ft.) by 20.

For instance, if your house has an area of 900 sq. ft., then you need an air conditioner with 18,000 BTUs (900×20).

If the aircon you’re using is too powerful for your room, you might consider getting an AC with fewer BTUs.

Air conditioner runs for a few minutes then shuts off – more troubleshooting steps you can try

Other than that…

Test the evaporator’s thermistor (temperature sensor)

The main work of this sensor is to detect when there is frost on the evaporator coils and signal the PCB to turn the compressor on/off.

As such, if this sensor is acting up, it will result in your air conditioner frequently turning on and off.

With that in mind, here’s how you can test it:

  1. While measuring the temperature on the sensor, test the resistance between its wire connections.

At a room temp of 20⁰C, the resistance will be around 6.1 kΩ. At 25⁰C, the resistance will drop to around 4.9 kΩ.

Pro tip: This might vary from manufacturer to manufacturer and as such, you might want to have the service manual nearby.

  1. Cover the thermistor with your hand. As the thermistor’s temperature rises, the resistance will start decreasing.

Now, if the reading that you are getting is not decreasing (or it doesn’t match the reading in the service manual), then the sensor is bad and you should replace it.

Test the motors and capacitors

Air conditioner runs for a few minutes then shuts off

Using a multimeter, test the amp draw of your condenser fan motor.

And, if your aircon has two motors, be sure to check the amp draw of the second motor (blower) as well.

Now, compare your reading to the nameplate value.

If the reading is not within this range, then it means that the motor is gone.

Luckily, the motor is a replaceable part – see current AC fan motor prices.

If the motor(s) is fine, proceed to measure the capacitance on the capacitor(s).

And again, compare the reading you get to the nameplate microfarad values.

If they do not match, there is a high chance that the capacitor is faulty.

But, before you fret, the capacitor is also a replaceable part and it comes cheap – view AC replacement capacitor prices on Amazon.

Is the refrigerant level below the required level?

why my ac automatically turns off and on

Here’s the thing: Low refrigerant levels will result in the compressor overworking.

In turn, this will overheat it and it will shut off (to cool) only for it to resume normal operation within a few minutes.

This will repeat itself continuously hence your AC will keep on turning on and off frequently.

Unfortunately, when it comes to the refrigerant, only an EPA-licensed HVAC technician can test the refrigerant levels (and recharge when necessary).

This is because the refrigerant is toxic both to you and to the environment.

So, you might want to have a HVAC pro come in and check the refrigerant.

My air conditioner keeps turning off and on by itself / Air conditioner runs for a few minutes then shuts off – final troubleshooting steps


The compressor might be overheating – check it

And when this occurs, it will shut off within seconds (or minutes) to cool down.

After cooling, it will turn on and repeat the same process.

With that in mind, you can first try to cool down the compressor to see if this fixes the issue.

Also read: How to cool down an overheating AC compressor

The control board might be faulty – visually inspect it

Most modern air conditioner systems come with a control board that regulates all the functions of the AC.

When this board fails, your AC might malfunction. And, one of the symptoms of the malfunction might be the AC frequently turning on and off.

Bearing that in mind, start by checking the wire harness connections – confirm they are securely connected.

Also, if any are frayed/burnt, be sure to replace them.

Something else: check for signs of burning – if there are, you might need to replace the board.

Pro tip: Since there is no way to test the board using a multimeter, you will rely on a visual inspection. And, at times, the visual inspection might pass but the board might still be bad. As such, if all the above solutions do not fix your AC, you might consider replacing the control board.

My air conditioner keeps turning off and on by itself – final thoughts

It’s not fairly uncommon for the compressor’s thermal switch to fail. And when it does, it might be frequently turning your AC on and off.

Luckily, you can easily test if this switch is to blame.

To do so, jumper the lead connections on the switch.

If the AC kicks in and runs smoothly, it means that the switch is bad and should be replaced.


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