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AC Won’t Turn On: Check This Before Calling an Air Conditioner Pro for Service

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It's a hot day and your air conditioner won't turn on! Before calling a repair service, there's a few things you should check. You may be able to save yourself some money and fix the problem yourself! "Use our quick navigation below to find the problem with your air conditioner"

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In this article we'll cover the six most common issues why your AC won't turn on. In many cases, you'll be able to resolve the problem yourself without calling a professional. However, keep in mind, if you're able to fix the issue, but the problem happens again, you should always contact a professional for service and repair. The root cause of the problem could be something serious, such as overheating or short circuiting

Do You Need an Air Conditioner Professional if Your AC Won't Turn On?

6 Most Common Problems Affecting Your AC Unit

Although, it's possible that the issue is serious and will require professional air conditioner repair. There's a good chance that the reason your AC unit won't turn on is because of one of these six common problems:

  1. Power Issues
  2. Thermostat
  3. Air Conditioner Needs to be Reset
  4. Shut-off Switch
  5. Inside Power Switch
  6. Clogged Condensate Drain Line

As stated above, it's critical that if the problem reoccurs to call a professional to do further troubleshooting. In addition, it's important to keep a regular HVAC maintenance schedule to avoid nasty surprises.  

AC professional working on outside unit

What to Do When Your Home AC Unit Won't Turn On

If your AC unit won't turn on, here are the 6 most common reasons why and what to do.

Power Issues

If your AC unit won't turn on, the first thing you should check is if there was a blown fuse or a tripped breaker. There's a good chance that the problem is a tripped breaker if the circuit was overloaded.

This is especially common during the summer months when temperatures rise and your air conditioner unit is working hard to keep you cool. However, it is also possible that a power surge caused your air conditioner to blow a fuse or trip a breaker.

Check the Thermostat

Before calling an air conditioning professional for repair, check that your thermostat is set to cool. Here's how:

  • Set the thermostat to COOL.
  • Then set the thermostat's temperature setting at least 5 degrees BELOW the current inside temperature.

Check the Breakers

If your AC unit still does not work, you should check to see if the breaker was tripped. There are 2 places to check:

Electrical Panel - Check your main electrical panel to see if there's a circuit breaker "tripped" (older homes use a fuse box). If the circuit breaker has tripped, simply turn it off and then back on.

Disconnect Box - Sometimes an AC unit will have a shut-off box nearby. Within the shut-off box there are typically fuses.

If one of these fuses has "blown" the air conditioner won't operate. It's important that you Do NOT replace the fuse(s) unless the power is OFF. Do NOT attempt replacing the fuses unless you feel comfortable doing so. If you don't know what you are doing, even changing the fuses can be VERY dangerous. 


If your air conditioner keeps tripping the circuit breaker or blowing fuses, you may have a more serious problem. You should contact an air conditioner professional for repairs.

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Lady adjusting ac thermostat on wall


When your air conditioner unit won't turn on, the problem could be your thermostat. In order to keep your home cool, your AC unit relies on the thermostat to tell it when to turn on and shut down. If you suspect a problem, check the following:

  • Check the screen on the thermostat. If it's blank, someone may have turned it off. Simply turn it back on and you should be fine.
  • If you are unable to turn your thermostat on, check and replace the batteries.
  • If after changing the batteries the screen is still blank, you may need to purchase a new thermostat. In most cases it's best to hire a professional to install it for you.
Chalk board drawing of a hand pointing to a reset button

Reset Air Conditioner

It may be that you simply need to reset your air conditioner. Not all AC units have a reset switch, so you may need to use the second method:

  • If you're lucky enough to have a unit with a "reset" switch (located near the outside unit) all you need to do is simply press the switch.
  • If you do not have a reset switch, you can turn OFF your air conditioner at the thermostat and wait for 5-minutes before turning it back ON.

If resetting your air conditioner solves the problem, you're good to go.

But if you find that your AC unit works for awhile and then you have the same issue again, you need to contact a professional for repair. You most likely have a more serious issue that needs to be addressed.

Red sign indicating the location of the AC power switch

Shut-off Switch

Many outdoor AC units have a shut-off switch. These switches are typically located near the unit and are inside a metal box mounted to the exterior of your home. They are sometimes labeled as an emergency shut-off.

If you recently had work done on your air conditioner, it's possible the workman forgot to flip the switch back to the ON position. The video below will show you how to check if your shut-off switch is the problem.

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Hand turning the ac power switch off

Inside Power Switch

The reason your AC isn't turning on may actually have nothing to do with the outside unit at all. The problem could be that the power to your furnace and indoor blower has been turned off.

In many cases there's a switch located near your furnace. It may be in plain sight or tucked away in a crawl space, closet, or attic. The switch can easily be mistaken as a light switch and someone may have accidentally turned it off. 

When the switch is in the OFF position, the blower is turned off. This can cause your inside unit to freeze and ultimately shut down your entire AC system.

We highly recommend labeling this switch to help prevent accidentally turning it off. 

AC repairman working on outside unit

Condensate Drain Line

The reason your air conditioner won't turn on could be because the condensate drain line is clogged. When AC units run, they create condensation, which is removed from the unit through a drain line.

When the drain line becomes clogged, a safety switch trips and shuts down your air conditioner. If this is your problem, you may be able to unclog the drain line with a shop vacuum. Sometimes the blockage can be removed from the drain line through suction. 

DeWALT 9 Gallon Poly Wet/Dry Vac

Shop Vacuum

The suction from a shop vacuum could help remove a clog in the AC unit's drain line.

Another possible cause could be that your system uses a condensate drain pump to remove the water from your home (not all systems do). It's possible that the pump isn't working. When the pump stops working the safety switch will trip, shutting the unit down.

Learn how to fix a drain line clog by watching the video.

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