Air Conditioner Turns On and Off Repeatedly

Air Conditioner Turns On and Off Repeatedly

Why does my AC unit keep turning on and off?

AC Keeps Turning On and Off RepeatedlyIf your air conditioner keeps turning on and off your AC system is most likely short cycling. An AC system may turn on and off repeatedly due to dirty, broken, or failing parts or for various other mechanical or electrical reasons.

The term short cycling refers to when an AC system’s cooling cycle terminates prematurely only to turn on again after a short time. Depending on indoor and outdoor conditions, this could mean that your system turns on and off every 5 to 10 minutes.

An air conditioner that is switching on and off repeatedly is bad for both homeowners and your AC system. It takes more power to start your AC over and over as opposed to when it’s running smoothly as it does in longer cycles. It also causes extra wear and tear on the mechanisms that work to turn on your AC. This can dramatically increase your electric bill and result in more repairs needed for your AC, so this is an issue you want to fix as soon as possible.

10 Reasons Your AC Keeps Turning On and Off & How to Fix It

Luckily, short cycling is usually an easy fix! Learn some of the most common reasons why your air conditioner keeps turning on and off and how you can stop your air conditioner from short cycling.

1. Thermostat Issues

Your problem may be as simple as your thermostat causing the short cycling, so when your AC system is short cycling, check the thermostat. While the thermostat may seem like one small component of your entire system, this device controls the temperature of your entire home, so it’s important that it functions properly.

If the thermostat is not sensing the temperature accurately and communicates misinformation, it will signal the air conditioning system to start and stop frequently.

If you notice your thermostat screen is blank or fading it may be low on batteries and losing power intermittently. This will cause your AC system to turn on and off when your thermostat loses battery power.

Solution: Try replacing the batteries and restarting the thermostat. If neither solution fixes your problem, call an HVAC professional to diagnose the thermostat.

2. Bad Thermostat Placement

Your thermostat measures the temperature of the air around it to determine when to turn your AC system on and off. Your thermostat may have inaccurate readings if it’s located:

  • Near a window and receiving direct sunlight
  • Close to a room that’s always hotter than the rest of the house, such as the kitchen or bathroom
  • Beneath supply air vents, receiving direct airflow

Any of these situations could cause your thermostat to receive inaccurate, poor readings and think your house is hotter or colder than it really is.

Solution: Move your thermostat to a better, more centralized location.

3. Dirty Air Filter

Clogged air filters are one of the most common causes of AC problems. A dirty air filter restricts airflow to your AC system and can cause multiple problems, including short cycling.

Solution: Check and replace your air filters if they’re dirty.

Related article: How Often Should I Change My AC’s Air Filter?

4. Dirty Condenser Coils

If your outside AC unit is turning on and off and you haven’t performed AC maintenance in a few years, it’s possible your AC’s condenser coils are caked in dirt and debris. Condenser coils are located inside the outdoor AC unit and release the heat from inside your home. If they’re clogged with too much dirt and grime, your AC system could overheat and turn off frequently.

Solution: Clean your condenser coils or have a local HVAC company perform routine AC maintenance.

5. Oversized Air Conditioner

Have you always had this problem? Or did it only start recently when you installed a new AC system?

A system that is too large won’t have an appropriate refrigerant cycle and will face numerous problems, like cooling your home too quickly and then turning off shortly after it turns on. This might sound like a good thing, but in reality, your home is cooling unevenly and your AC will turn back on again sooner than it should need to.

Not only are these issues inconvenient, but they can cause bigger problems for your home, such as:

  • Higher energy bills: Turning your AC on and off repeatedly uses more energy
  • More repairs: Not only does short cycling use more energy, but it also puts more wear and tear on the parts in your AC
  • Shorter lifespan: More wear and tear means the average life expectancy of your air conditioner will be shorter.

Solution: Use an AC sizing calculator to approximate your system size requirements or contact a local HVAC company for a second opinion on the installation.

6. Refrigerant Leak

If your AC system has a refrigerant leak, your air conditioner could be too low on refrigerant. Refrigerant is a coolant that cycles through your AC system, absorbing heat and cooling down the air inside your home.

It’s a common misconception that refrigerant is used up as part of an AC system’s cooling process. But the truth is low refrigerant levels are caused by small holes that allow the refrigerant to escape.

When your AC system is low on refrigerant, the compressor will malfunction and shut off your compressor because the pressure is too low. Then, when your compressor is off, the pressure will rise again and it will turn back on. This creates a short cycle that causes massive amounts of wear and tear on your AC system, potentially resulting in parts going bad or system failure.

Solution: Refrigerant leaks can be dangerous, call a local HVAC company to find and fix the leak.

7. Compressor Failure

Just like when there’s a refrigerant leak, if your AC compressor is overheating, malfunctioning, or starting to fail, it will result in your AC system shutting off frequently and starting back up shortly.

Solution: Contact a local AC repair company to diagnose and replace your AC compressor.

8. Frozen Evaporator Coils

If your AC system has airflow issues or a refrigerant leak, it’s possible your evaporator coils are freezing up. When this happens, your AC system or sometimes just your outside AC unit will turn off until the ice thaws and then turn on again.

Solution: Check your outdoor AC unit for ice buildup, if you’ve already checked your air filters, then you likely have a refrigerant leak and will want to call a local HVAC company to find and fix the leak.

Air Conditioner Turns On and Off Right Away

Is your air conditioning system turning on and off right away, after only a few seconds or minutes of running? If your air conditioning unit turns on and then off immediately then you most likely have problems with the electrical components or the run capacitor.

9. Electrical Problems

Electrical problems are a common cause of short cycling. Often times, there may be an issue with the electrical supply line or the capacitor could be broken or failing, but your AC system could also have an electrical issue due to the thermostat, electrical connections anywhere in the system, or the circuit boards.

Solution: Call a local professional electrician. Electrical problems are not only difficult to diagnose but diagnosing an electrical problem can be dangerous for even the most knowledgeable homeowners.

10. Bad Run Capacitor

Your AC’s run capacitor gives your AC system the initial boost of energy it needs to turn on and also provides continuous power so your system can keep running. When this part starts to go bad it can result in intermittent power being supplied to your AC, causing it to turn off unexpectedly and then back on.

If your outside air conditioner turns on and off right away, then chances are there’s a problem with your run capacitor.

Solution: Contact a local HVAC company to diagnose and replace your AC capacitor.

39 Replies to “Air Conditioner Turns On and Off Repeatedly”

    1. Review all electrical connections, this turning on and off continuously is more to me, due to an almost burnt connection or wires that still passes power but the compressor stops internally to protect itself of worst damage.

  1. Half of your solutions are just to call someone else. Thats not the solution. Thats just asking someone else to find the solution.

    1. Hi Mike, thank you for your input. I’ve updated a few solutions to provide more information than to just call an HVAC company. But the reality here is some of these problems are things you will want a professional to handle, such as refrigerant leaks. Also, using off-brand parts in repairs or performing DIY fixes as an unlicensed contractor can void your warranty which can end up costing you in the long run.

      1. If u try and fix yourself and don’t have correct equipment ie: gauges. U could cause major failure and completely destroy the compressor. Lots of newbies make mistakes like not evacuating system or back flowing oil into system. In those cases you may have to buy a brand new unit..
        Call the pros and make sure they r HVAC techs, not apprentices!!!

    2. In the air conditioning field the solutions can be as simple as detecting a burnt connection, a low voltage reading missing, or dirt in a coil that’s blocking the air of passing through and those are visible ways to get to problems that need us to touch hot cables that can kill someone, or touching or handling a coil that can be a delicate part that needs experience handlers so there’s no more issues. I feel the publisher can tell you all the solutions but, this equipments are hooked to high voltage lines and under pressure freon lines that can be dangerous to work for someone that doesn’t have the experience to fix air conditioning. S/he expects you to be able to find someone serious and professional that will bring you the solutions an peace of mind because we don’t know how capable you are to handle the mirada of possibilities why an a/c system fails besides, they’re several systems wired differently. Believe me, they get complicated.

  2. My brother and I want to make sure that all the appliances at his beach house work properly before moving in for another vacation stayover. It really helped when you noted how faulty thermostat placement can have direct effects on the ACs performance we found one particular AC unit near the kitchen that ends up producing less consistent air and we wondered if the kitchen had anything to do with it. I’ll be sure to consult an air condition contractor and see what advice he has for us before we settle in for vacation. Thank you!

  3. If the ac is turning off and on repeatedly, then it must need to take ac repair service or should consult the ac repair expert. Otherwise it can be a major problem later.

  4. Thanks for pointing out that there might be a problem with the air filter if my air conditioner is turning on and off randomly. I am quite worried about my air conditioner breaking down in the middle of summer because I literally can’t sleep at night due to the heat. I hope that when I call in an air conditioner repair service, it wouldn’t take a whole day to get it fixed.

  5. Any additional thoughts for an AC that short cycles (30 seconds on, 5 minutes off – air handler stays on for an additional minute or two) BUT after maybe 30 minutes of this decides to stay on and work right? (not air filter, but I have been doing some carpentry next to the AC unit so there could be more dust than usual in there – is it safe to hose it down/pressure wash it?) Thanks!

    1. Hi Jeff,

      It’s hard to say without being able to diagnose the unit but it sounds like your AC struggles to turn on and stay on. When you say the “air handler stays on for an additional minute or two”, do you mean you the fan inside is still blowing air throughout your home or that you can hear the outside condenser unit still running? Or is it just the outside unit’s fan continuing to spin while the unit is off? The answer to this could help determine the cause. In either case, the issue may be related to the run capacitor, the fan motor, or potentially another part malfunctioning or overheating, especially if you noticed this recently during the hot summer months when your AC unit is working it’s hardest.

      To be safe, I would have an HVAC technician check this out right away because if one part is starting to malfunction it can cause extra strain and wear and tear on the other parts, resulting in more parts failing or total system failure.

      Excess dust on the outside condenser from the carpentry work could be contributing to parts overheating if it’s impeding airflow on the unit, just like a clogged air filter. It’s safe to gently hose down your condenser unit, but do NOT use a pressure washer as the force of a pressure washer would almost certainly bend the fins (which would impede airflow) and potentially cause damage to the coils or other parts in the unit.

  6. My ac is working fine then when it gets to the set temperature (78) it turns off like it’s supposed to but won’t turn back on even if it’s set lower (77) than what it is (82) then the next day turns back on by itself back at (77)
    What could be the problem

    1. Hi Adriana,

      That’s an odd issue. My initial thought is that maybe you have a partially clogged AC drain line and the float switch (a safety sensor switch) is sensing water which will turn off your AC system to prevent damage. Next time your AC won’t turn back on, check the drip pan and see if there’s water pooling. For more information, check out this blog on clogged AC drain lines: https://gabesguides.com/hvac/how-to-unclog-clogged-ac-drain-line/

      If that isn’t the problem then maybe your AC system is leaking refrigerant or low on refrigerant which could cause your AC to shut off because the pressure is too low. It’s also possible that your coils are freezing over due to the refrigerant leak and your AC isn’t turning back on until the ice thaws. Check your outside AC unit for the presence of ice on the refrigerant line. For more information, check out this blog on refrigerant leaks: https://gabesguides.com/hvac/refrigerant-leaks/

      And if none of those are the problem and you’re sure it’s not an improper setting on the thermostat that’s causing your AC not to turn back on, then I’d suggest you have someone come out and look at the system because that is not normal operation and a part may be malfunctioning or starting to fail and the problem will only get worse.

  7. My outside fan short cycles. I’ve checked the capacitor, cleaned the coils, and changed the air filter. If I let it run it’ll freeze the pipe so I know the condenser is working. What can it be?

    1. Hi John,

      If the pipe that’s freezing over is the refrigerant line, it sounds like you may have a leak or micro leaks. Since refrigerant can be dangerous I’d recommend having an HVAC professional come out and diagnose the problem.

      1. I have a similar issue.

        -new heat pump system
        -worked perfect since it was installed 4 months ago
        -now fan and compressor come on for several minutes then they stop and do not restart for approx. 45 min.
        – cleaned filter, cleaned coils, changed out the capacitor, switched thermostats. (Don’t have tools to check refrigerant.)

        What else could I check or replace?

  8. I have tried 3 different A/c’s and the compressors just won’t stay on for a prolonged period of time. I thought my first one died, got a new one…. compressor cycles on/off, took it back, got a new one same thing. 5000 btu’s. Could it be the electrical?

    1. Hi MJ,

      Are you replacing just the AC compressor part or the entire condensing unit? Either way, it’s hard to diagnose the issue based on the information provided. Any number of things could cause a single part or the whole unit to stop working, as you can see from the 10 examples I listed in the article.

      If you’re only replacing the compressor and it’s repeatedly having issues then I’d guess another part, like the capacitor, may be failing and causing widespread issues. If you’re replacing the entire condensing unit and running into problems then I’d suggest you have an HVAC technician inspect your AC system.

  9. I have had my a/c unit recently charged with freon last week, since then we left for 4 days and when we got back I noticed my outside unit turns on and off within 2-3sec. And it does that randomly 2min, 3min, sometimes 5min. What do you think is the issue here? I know the capacitor is new.

    1. Hi Jerrson,

      Losing freon is not a normal part of an AC system’s operation, AC systems do not lose freon unless there’s a leak. I’m guessing whoever charged your AC with freon did it as a band-aid fix to get a few more years out of your AC, which is okay if other parts aren’t failing or need to be replaced. It’s concerning that you also replaced the AC capacitor recently too. I would have them come back and check out the unit or call another AC company for a second opinion.

      Depending on how old your unit is and how expensive the repairs are, you may want to consider replacing it instead of dropping more money into repairs. Check out this post about when to replace your AC system for more information: https://gabesguides.com/hvac/when-to-replace-hvac-system/

  10. Outside unit runs for one minute then turns off for one second just enough time for the contactor to open and close for another round of one minute and one second off. Inside blower works the whole time. I turn off the outside breaker and the inside unit breaker for about ten minutes and after I turn them back on the unit performs fine for a few days then it happens again. Average temp outside is in the 90’s thermostat set to 76. The unit is eleven years old and very clean and I have installed a new run capacitor. I change the filter every two months. Replaced contactor about seven years ago also. Problem still exists.

    1. Hi Mark,

      It sounds like you take great care of the unit and know what you’re doing. Most of my guides are written for the everyday homeowner, so I’d typically advise contacting an HVAC technician to diagnose the unit at this stage, they’ll be able to run electrical tests on the parts and check for visible damage. I’d say since the run capacitor is new, double check that you used the right replacement part first. It could also possibly be an issue with the compressor or if you have a start capacitor in addition to the run capacitor, look there. But again, at this point I would suggest calling in a professional.

  11. The A/C unit inside stops and starts at 1-2 second intervals only when it rains heavily, then after doing it several times goes back to normal. A highly recommended HVAC guy checked it and found the compressor capacitor not bad but weak, so he replaced it. Other than that, nothing else wrong with the system. But, the cycling still happens every time there’s heavy rain. Exactly the same thing it was doing before.

    1. Hi Robert,

      I would guess that maybe the heavy rain is causing some standing water or flooding and possibly your AC shuts off as a safety prevention feature but it’s hard to say for sure without inspecting the unit during heavy rain when the issue is present. I would call the HVAC technician you used and let them know the problem still occurs.

  12. I am having this same problem but I have a portable window air conditioners. I just bought it less then 2months ago, it worked perfectly. Three days ago it started this on and off thing makes me crazy and it’s can’t be good for it. I still there a way I can fix this

  13. Does anyone know why my air conditioner runs for about 15 minutes then shuts off for only about 4-6 minutes then comes back on? This even happens after the sun goes down until about after midnight? It use to run about 50% of the time but now due to it only turning off for just a few minutes it’s running a lot more. The compressor is only 8 years old.

  14. My window unit ac (18,000 btu) that I just bought 3 months ago for $630.18 is turning on and off changing fan settings as well as mode settings. The filter light is on but I have cleaned the filter which was barely dirty at all and the light won’t go off. I first thought maybe the remote was shorting out so I removed the battery from it but it continued to act up. It’s blowing cold air and isn’t froze up inside or out. What is my problem?

  15. The inside fan comes on and runs for a few minutes then the outside unit will kick on. Sometimes it takes several minutes for it to start but once it does, it works fine. Very frustrating and also (at times) hot as I am in Texas! Please help.

  16. Always try the easiest / least expensive solutions first:
    1) Change the air filter
    2) Thermostat Issues (Battery, wiring…)
    3) Clean Condenser Coils
    4) Thermostat Location
    5) Clean Evaporator Coils
    6) Call repair man for service

  17. I replaced my AC unit’s switch and run capacitor. The AC now works again. However, I noticed that the AC unit runs for a minute or so, turns off a second and starts again before the fan comes to a complete stop. It doesn’t stop completely! Any ideas!

  18. I had no idea that insufficient refrigerant levels can cause your AC’s compressor to stop functioning properly. My wife and I have been noticing a small puddle forming under our window air conditioner, and I am worried that refrigerant may be leaking from it since I accidentally dropped it when I tried installing it by myself last month. We’ll find an expert that can help us fix our unit.

  19. I didn’t know that your AC unit may be turning on and off if dirt has accumulated on its condenser coils. My wife and I have noticed that our air conditioner shuts off whenever we try to cool off our living room for more than 10 minutes, and we want to repair the unit so that we can host a dinner party for my wife’s birthday next week. We’ll be sure to find a professional that can take a look at our AC.

  20. If my air conditioner froze and I turned it off. But when I turned it back on after a couple hours it turns on and off in seconds is that bad?

    1. Hi Franchesca,

      If your air conditioner froze over then you’ll probably want to call an HVAC company to check for refrigerant leaks. I’d guess that the ice didn’t fully melt yet off your AC’s internal components or that the excess condensation from all the ice melting triggered your AC’s safety sensor switching and caused your AC to turn off. The bigger issue here is the possible refrigerant leak and you’ll want a certified HVAC technician to diagnose and fix that.

  21. We had a brand new unit, air handler, and thermostat installed. All was working fine for about 3 mos. Now the AC comes on, runs for 3 minutes, then shuts off and goes into delay mode.
    Thermostat flashes “cool on” but the system is not running. If I switch the thermostat to “fan” vs “auto”, nothing happens. Blower does not come on.
    My AC tech, via text, had me remove the float in the air handler to see if it would come on and stay on, it did not.
    We replaced the air filter and thermostat, same issue.
    Drain line appears to be clog free as water is dripping from it.
    It comes on for exactly 3 minutes, I set a timer, then kicks off.

  22. Since hurricane Sally power has been restored in my home but now my a/c keeps “short cycling” inside the home? What do u think would have caused this?

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