Air Conditioner Won't Turn On - 5 Troubleshooting Steps for a Broken AC

Air Conditioner Won't Turn On - 5 Troubleshooting Steps for a Broken AC

If your air conditioner won't turn on, it can be frustrating...to say the least.  Those of you who have read our articles, know that we started as a small, U.S. Veteran-Owned heating and air conditioning company that built our reputation on giving honest, straight answers...our articles are no different.  If your air conditioner won't turn on, it's important to troubleshoot a few key things before you call in an HVAC technician, as this can save you time and - more importantly - money.  There are some serious problems that can cause these issues, but typically, when your AC won't turn on, you have about a 70% chance of solving the issue yourself.  In this article, we will discuss some common issues that can keep your AC from turning on, how to reset your air conditioning unit, and hopefully, learn a few key steps to take if your AC isn't working.


Air Conditioner Won't Turn On - The Basics

I know that some of your are moonlighting as HVAC technicians, but this is even for you do-it-yourselfers...when an air conditioner won't turn on, you'll need to understand some key HVAC terms before we can explain how to troubleshoot it.  Otherwise, how the hell will you know what we are talking about?  Granted, my wife argues that I don't even know what I'm talking about, but I digress...your AC isn't working; let's discuss some common language.

Key Terms to Know When Your AC Won't Turn On

air conditioner won't turn on - AC troubleshootingWhen your AC won't turn on, we will need to check a few things ourselves before we call in the professionals.  But how can I tell you to check your "condensing unit," for instance, if you don't even know what that is?  This is the crash course...

  1. Split AC Unit - A split unit is an air conditioner that has two parts: one inside (in a closet, attic, or utility room inside of your house), and an outside unit.
  2. Packaged AC Unit - A packaged unit is just one big unit that has both of these parts, and is typically located on the roof.
  3. Condensing Unit - A condensing unit (or "condenser") is the boxy-looking part of a split AC unit that is outside.
  4. Evaporative Coil - An evaporative coil is the part of a split AC unit that is located inside of your home, or in a utility room or attic.
  5. Thermostat - Ok, come on...you have to know what this is, right?  You'd be surprised...the thermostat is the control panel for your air conditioner that is located on the wall of your house somewhere.
  6. Air Filter - Your air conditioner has an air filter that is located somewhere that is usually (not always) easy to change.  You should be changing this every three months, so if you have no idea what the hell I'm talking about, then I think I just figured out the problem...just saying.

For more extensive explanations of these topics, try:

Why Your AC Won't Turn On - The AC Crash Course

I'm not going into the weeds here, but your AC won't turn on for a reason.  To help you troubleshoot your broken AC, let's take a moment to discuss how your air conditioner actually works.  

An air conditioner works by compressing a refrigerant, which, as we all know from the Joule-Thomson Effect (because we all paid attention in physics, right...?), will cause it to heat up.  If we were to do this outside of your home, the refrigerant would release heat...heat that was once inside your house.  This is what the condensing unit on your AC does, and you'll need to know this if your AC isn't working.

So, since everyone here is really smart, I'm sure we've figured out that if we were to expand the same refrigerant, it would then get really cold, right?  If we did that inside of our house, that would cause the air in our home to get colder.  That is what the evaporative coil in your home does.

  • AC for Dummies - Air conditioning works by expanding gas rapidly inside of a coil, causing the air inside of your home to cool when it is blown over this coil.

So why does this matter?  Well, if your AC won't turn on, it's because one of these things isn't happening.  Don't get too lost...just remember that air conditioners are really simply pieces of machinery...I mean, HVAC technicians aren't the brightest, right?  Hey, wait...

Also try:

Air Conditioner Won't Turn On?  How to Troubleshoot Your Broken AC

Look there are only a few reasons that your air conditioner won't turn on.  So, let's take a look at some of them and get your AC up and running again.  It's hot, right?

air conditioner won't turn on - AC troubleshooting flow chart

Step 1: Air Conditioner Won't Turn On - Check Your Thermostat

I'm speaking now in the voice of Michio Kaku..."imagine, for a moment, that most people are stupid..."  

I know it seems silly, but if I told you how many times I used to get called out to a house because an AC wouldn't turn on, to find out it was actually an overzealous wife waging a cold war (pun intended?) on her husband for keeping the temperature too low...you'd be surprised.

Make sure that your AC thermostat:

  1. Has power.  
  2. Is set to COOL.
  3. Has the temperature set at least 3-degrees below the current room temperature.

If your thermostat is battery powered, the batteries might need to be replaced.  Otherwise, ensure that some rodent hasn't eaten through the wires!  Make sure that it is in COOL mode, and that the temperature is set below the current one.  If any of these are not true, then that's why your AC won't tun on!air conditioner won't turn on - Michio Kaku quote

Step 2: Air Conditioner Won't Turn On?  Check Your AC Air Filter

We discussed how your AC works, so now let's imagine for a moment that something was keeping the air in your home from going over the coil that is supposed to be cooling the air.  Wouldn't that coil get colder and colder without the air in your home heating it up?  If it got too cold, eventually it would freeze up and block air flow in your home.

If you didn't follow me, that's ok.  If your air filter is clogged, sometimes your AC won't turn on.  Usually, it results in your air conditioner running, but not cooling your home, but it can also keep your AC from turning on at all if it's bad enough!

If your AC will turn on, but isn't cooling your home, try:

Your AC air filter is typically located at the air return for your air conditioner (the big grille that sucks air into it, instead of blowing it out), or at the evaporative coil itself (remember, that's the inside unit).  Go check this filter now!

  • If your AC air filter is clogged, then replace it.
  • If your AC air filter isn't clogged, then replace it anyway!

AC air filters can be clogged but still look clean...the only way of knowing if it is fresh is to replace it, and do so every three months at a minimum!

Step 3: My AC Unit Won't Turn On - Check Your Circuit Breakers

Your AC won't turn on if you have a tripped circuit breaker (shocker, I know).  But why do circuit breakers trip?

A circuit breaker is a safety feature, and it is designed to click the power off to an electrical component of your home (like your air conditioner) if there is some type of power surge.  Most times this is just a harmless power surge in the grid.  Or, your husband just turned on a high-amp power tool - ahem...not that I've done that - and tripped the breaker.

  1. Locate the air conditioner circuit breaker marked on your home's main power distribution panel...the big circuit breaker panel located inside our outside of your house.  It will be marked as "A/C," "HVAC," or "air..." something like that.  If none of your circuit breakers are marked...haha!  Have fun!  Turning off the wrong one won't hurt anything, but it'll take you a bit of the process of elimination to figure them all out...just saying.
  2. Turn this breaker all the way off.
  3. Wait a few seconds.
  4. Now turn the breaker on again.
  5. Check your air conditioner.

There are a couple of important tips to keep in mind when dealing with circuit breakers:

  • Circuit breakers can look ON, even when they are tripped.  So, make sure that you turn it all the way off, then back on again.
  • Only reset a circuit breaker ONCE!  If it keeps tripping off, that's because there's a problem and you run the risk of starting an electrical fire if you keep turning it back on.  If it keeps tripping, call out an HVAC technician; you're done.

Step 4: Air Conditioner Isn't Working - Check Your AC Drain Pan

Underneath your air conditioner is a drain pan, which is meant to accumulate any residual condensation that your AC wasn't able to drain out.  If your AC drain pan is full, it may have triggered the float switch; a switch designed to stop your air conditioner from flooding your house with residual condensation.  Good idea, right?

AC won't turn on - check drain pan

Over time - especially in humid climates - these drains can become clogged, which will then spill into your drain pan.  Your drain pan should also have a secondary drain (to keep this from happening).  Once your drain pan drain is clogged and your drain pan itself is full, this should trigger your float switch to turn your AC off.  Your AC won't turn on until you clean out your drains, and get the float switch back into the DOWN position.

Typically HVAC technicians use compressed air to clear out the drains during servicing (ahem...hint, hint), but you can actually clear them out by cupping your hands together and blowing really hard...it's just that it's disgusting.  Don't give yourself a heart attack.

For those of you who are do-it-yourselfers, here's an article to prevent this from happening again:

Step 5: AC Won't Turn On - Check the AC Shutoff Switch

When your air conditioner won't turn on, do you ever ask yourself, "did I turn the AC switch off?"  Probably not...but that might be exactly what you did.air conditioner wont turn on - check AC shutoff switch

Air conditioners and furnaces are often installed with an ON/OFF switch that looks just like the light switches in your home, only this switch is there so that lazy HVAC proletarians - like me - can easily remove power while troubleshooting and servicing.  

  • Look at the inside portion of your air conditioner, and all around it for a light switch.  
  • It should be relatively close to the AC system itself.
  • When/if you find one, switch it (UP isn't always ON, don't ask me why...) and try your AC again.

Although this is one of the easiest things to check, we have it last on our list because, let's face it, if you knew there was a switch there, is it really probable that you switched it off and didn't know about it?  Probably not.  

However, when kids are right around two-years-old, they just love to open random doors and flip switches...in fact, my lights have gone on and off three times while I've been sitting here writing this; thank you, daughter.

What to Expect Next if Your Air Conditioner Won't Turn On

If your air conditioner still won't turn on, then I'm afraid that it's time to call in the professionals.  The nice part is that you have a list of things to tell them it isn't (they are going to double-check though...ahem...just in case...).  

Here are some tips to keep in mind when they come out to look at your AC:

  • Use a reputable contractor.  Make sure they are certified and licensed.  If you don't know of one in your area, use one of our ASM-approved contractors; they'll take care of you.

If your AC isn't working, it may be time to replace it.  Here are a couple of related articles to get you going; do your research:

Since we ruled out most of the simple AC issues, it'll probably be something like a seized blower motor or a compressor (sorry).  The average price for these types of repairs - since you asked - are a bit pricey.  Take your heart medication, and we'll have a look in our next section.

AC Won't Work?  Here Are Some Average Air Conditioner Repair Costs

Per Data Collected by ASM-air.com

  • Compressor replacement: $1150-$1520 (depending on size and type)
  • Fan motor replacement: $210-$420
  • Refrigerant leak detection & repair: $227-$937
  • Circuit board replacement: $230-$610
  • AC compressor repair hard start kit: $100-$150
  • Replace blown fuse, circuit breaker or relay: $55-$255
  • Thermostat replacement: $50-$300 (depending on model)
  • AC refrigerant recharge: $155-$650 (refrigerant is expensive)
  • Evaporator coil replacement: $710-$1300
  • Condensate pump replacement: $88-$212
  • Capacitor or contactor replacement: $90-$400
  • Entire new AC system, see: HVAC Installation Cost

If It's Time to Replace Your AC, Don't Overpay:

If you've done everything you can (including calling a professional) and your air conditioner still won't turn on, then it might be time to replace it.  Make sure you pay a fair price...here's how:


Final Thoughts on When Your Air Conditioner Won't Turn On

When your air conditioner won't turn on, it can be frustrating and uncomfortable.  But hopefully, this article on troubleshooting when your AC won't turn on was helpful at getting you to where you need to be.  If not, then it's time to call in a pro.  We do have a list of ASM-approved contractors from around the country, so don't hesitate to give them a call; they'll treat you right.  This is where I tell you that you should contact us with any questions you might have...but I'd really rather you didn't!  If you have any suggestions on what we could have done better - seriously - please feel free to place them in the circular file located next to my desk...


Tim K.
About the author
Tim K.

The University of Virginia - 2005 / The Wharton School of Finance - 2016 / U.S. Naval Aviator 2005-2015. At All Systems Mechanical air conditioning and heating, we believe that the experience our clients have is every bit as important as the products they receive. Simply put, our results speak for themselves, and we'd be happy to help. If you're in the market for a new AC or furnace, make sure that you get a fair price! Try our online calculator; click the tab on the top of this page for more information.

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