Whether it’s your typical hot summer or you’re in the middle of an unexpected heatwave, fixing an AC blower that keeps turning off and on is critical.

For you and your system.

I say it’s critical for your system because there’s a chance your system is short cycling, and if that’s the case, something needs to be addressed.

Below, I’ll explain all the reasons behind an AC system the keeps turning off and on and what you can do to fix them. So that you can get your house back to the cool temps you crave.

First, let me explain what short cycling means, then I’ll list out causes and fixes. So read on!

What Does Short Cycling Mean?

Heating and air conditioning units are meant to cycle on and off. This simply means they don’t just run indefinitely, which could burn out their motors.

Depending on how extreme outdoor conditions are, your system should cycle off and then on every 10 to 20 minutes. So they’ll run for 10 minutes then shut off and wait another 10 minutes or so to start again.

The time depends on how long it takes the temperature to rise or fall against what your thermostat is set to. Again, that will depend on outdoor temps.

Short cycling is what occurs when this cycle is happening faster than it should. Since this is bad for your system, they have a failsafe built in, and will shut your system down—usually for about 5 minutes.

10 Reasons Why You Need to Fix an AC Blower That’s Turning Off & On

Here are several reasons why your system is short cycling and how to fix it.

1. Your Air Conditioner is Oversized

Bigger is not better. At least in this circumstance.

If you’ve been dealing with short cycling since you had the unit, this could be the cause. An oversized compressor will drop the temperature in your home too quickly, which, ironically, is a bad thing. It can lead to:

  • More energy consumption/higher bills
  • Increased wear and tear meaning more repairs
  • Decreases lifespan

How to fix it: Unfortunately, there is no quick fix for this. If you want the problem to go away, you need a smaller unit. What you can do is hire a pro to properly calculate the size you need, which will at least rule out or pinpoint your problem.

male checking HVAC unit
Hire a professional for sizing your HVAC unit properly

2. Problems with Your Thermostat

Think of your thermostat as the hub of your HVAC equipment. So when something goes wrong, it’s often the first thing you should check. Remember, this is the device that calls for hot or cold air—it’s what regulates your indoor temperature.

Your thermostat may be sensing inaccurate information which is causing it to shut down your system prematurely.

Check for a blank screen or a screen that seems to fade in and out. If so, you may have a power issue.

How to fix it: Replace the batteries in your thermostat.   New batteries and the reboot that happens when you replace them might fix the problem. If you have a blank screen and this didn’t work, call a pro.

3. Thermostat Placement

Did you buy a new thermostat and decide to place it somewhere else than where the original was? This might be the cause of your problems.

A thermostat could have inaccurate readings, which would make it shut your system down if it was in any of the following places.

  • Close to an uncovered window that gets direct sunlight
  • Close to or in a room that generates heat such as kitchens and bathrooms
  • Directly above or beside a supply vent

If your thermostat thinks the room is hotter than it is, it will lead to inaccurate readings and potentially turn your AC off.

How to fix it: Find a better location for your thermostat, typically something located centrally.

4. Clogged Air Filter

Are you keeping up with your regular maintenance, which includes changing or cleaning the filter?

If your filter is dirty, it can restrict airflow to the point that your system starts to short cycle.

dirty air filter
Dirty air filters can cause various problems.

How to fix it: Check the maintenance requirements on your filter and follow the replacement schedule.

5. Dirty Condenser Coil

The condenser coils are inside the compressor—your outside unit. If you leave it uncovered, it stands unprotected in the elements year-round. This means the coils can become caked with all sorts of debris. This could make your unit frequently overheat and shut down.

How to fix it: Remove the cover from the condenser and clean the coils. You can either do this yourself or hire a pro.

6. Refrigerant Leak

If you have a leak, it can cause your compressor to shut down since the pressure in the line is too low. Once it builds back up, your compressor will come back on.

Your system will short cycle, turning your AC off and on continually.

How to fix it: This is not a fix for the homeowner. All refrigerant issues need to be handled by a certified HVAC professional.

7. Compressor Failure

Compressors have a life cycle, and they will eventually break down. Usually on the hottest day of the year!

As it begins to die—it overheats, it malfunctions, and so on—it will begin to short cycle. Pay attention to the length of the cycle. If it’s cycling every two minutes or so, you likely have a system failure.

How to fix it: This will require a pro. Have the unit diagnosed. There may be a part that can be replaced, but you may need a new unit.

8. Frozen Evaporator Coils

Evaporator coils need sufficient airflow. Closed registers, dirty filters, and more can reduce airflow. This means your coils—which are cold to begin with—don’t have enough heat to absorb and they freeze up.

How to fix it: If you have found a buildup of ice in your compressor, try addressing things like filters and closed registers first. Once you’ve ruled that out, have a pro come to check for refrigerant leaks.

Additional Causes for an AC Blower Which Keeps Turning Off & On

The above issues dealt with a system that turned on and off after several minutes. But what if yours system is turning off as soon as you start it? Here are some typical reasons.

9. Electrical Issues

This is fairly far-reaching. You could have issues with the wiring itself, the capacitor, the thermostat, or the circuit board.

How to fix it:  If your problems are electrical in nature, you will need to contact a professional.

10. Clogged Drain Line

If your drain line backs up or gets clogged, most systems have something called a float switch. When it engages, it will shut your system down. If you have no air circulation, even when you switch your thermostat to auto, you may have a drain line issue.

How to fix it: First, rule out problems with your thermostat and any electrical problems. When you’ve done that, follow this excellent tutorial on how to unclog and clean a drain line.

Conclusion

As you can see, there are a number of reasons why your AC blower could be turning on and off.

Some of them may be as simple as needing to replace the batteries in your thermostat or repositioning your thermostat. Others may require an electrician or HVAC professional to diagnose and fix.

Hopefully, there was enough info here to either help you fix the issue or guide you in the right direction. Thanks for reading.

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