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

Air Conditioner Won't Turn On

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"

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

Although, it's possible that the issue is serious and will require professional air conditioner repair. There's a good chance that it's one of six common problems.

  • Power Issues
  • Thermostat
  • Need to Reset the Air Conditioner
  • Shut-off Switch
  • Inside Power Switch
  • Clogged Condensate Drain Line

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. Its important to keep a regular HVAC maintenance schedule to avoid nasty surprises.  

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

AC professional working on outside unit

The 6 Most Common Problems Affecting Your AC Unit

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.
  • Do NOT replace the fuse(s) unless the power is OFF and you feel comfortable doing so.
  • Unless you know what you are doing, this can be very dangerous.

This video will take you through what to do when your air conditioner unit won't turn on:

Important Maintenance Disclaimer

Caution: 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

There are two methods to reset an air conditioner.

  • 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 within 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. 

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. The problem could be that the power to your furnace and indoor blower has been turned off.

Typically there's a switch located near your furnace. It could 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 va​​cuum. Sometimes the blockage can be removed from the drain line through suction. 

If your system uses a condensate drain pump to remove the water from your home, it's possible that the pump is not working. When the pump stops working the safety switch will trip, shutting the unit down.

How to fix a drain line clog:

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