Why would my AC unit not be kicking on?

Author: Arvid Rosenbaum  |  Last update: Sunday, June 29, 2025

Common Reasons Why Your Air Conditioner is Not Turning On Resetting your thermostat is often all that's necessary to get it working again. A tripped circuit breaker is another common reason why your AC won't turn on.

What would cause my AC to not kick on?

Power issues: A tripped circuit breaker or blown fuse in your home's electrical system will prevent your AC from starting. Thermostat problems: Make sure you have your thermostat set to “cool” and the temperature is set below the current temperature in the room.

Why isn't my AC unit turning on?

If the wires are frayed, not connected, or dirty, your air conditioner will not be able to turn on. Another common problem is a faulty thermostat. If the thermostat malfunctions, it will not send the signal to the air conditioner to turn on.

Why is my outside unit not kicking on?

The main reasons your AC unit outside is not turning on could be something that has tripped the circuit breaker, something is blocking the fan's airflow, or the condensing unit is damaged. Other potential issues could be the thermostat isn't set correctly or the compressor could be malfunctioning.

Why is my thermostat working but AC not turning on?

If your thermostat is set to cool but your AC isn't turning on, there could be several potential causes ranging from a simple tripped breaker to more complex refrigerant or compressor issues. Start with the basics, like checking the thermostat settings and power supply, and work through more detailed troubleshooting.

Outdoor AC Unit Not Running, Not Turning On! Top 10 Problems!

How do I get my AC to kick on?

Follow these steps.
  1. Step 1: Check the thermostat. Make sure that your thermostat is set to "cool" and not "heat" (if it's set to heat, your AC won't turn on no matter what). ...
  2. Step 2: Check the air filter. ...
  3. Step 3: Check the circuit breakers. ...
  4. Step 4: Clear the condensate drain.

How to tell if an AC fuse is blown?

Blowing the fuse cuts the power to the unit to prevent electrical damage. If your AC has shut down and won't start again, especially if you've noticed odd electrical behavior immediately before the shutdown, chances are the fuse has done its job and will need to be replaced.

How do I force my AC unit to turn on?

Look for a RESET Button.

Some systems have a RESET switch on the outside unit. You can push this and see if it helps. If your unit does not, you can turn off the system at the thermostat, wait 5 minutes, and try again.

How to tell if an AC capacitor is bad?

A sure sign of a bad AC capacitor is a humming sound from within the access panel. Any humming noises indicate a problem with the air conditioning system or the components of the AC unit. Try turning the power on and off again to see if it was a one-time issue with the motor or a recurring problem.

How do I reset my outside AC unit?

In AC systems, the air conditioner reset button is on the outside unit's lower edge, typically close to the ground. Some models have the reset button located behind the service panel, which may require tools to remove. Reset buttons are usually red or yellow with a clear “reset” label.

How do I know if my thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken
  1. The Thermostat Has No Power. ...
  2. The AC or Furnace Won't Turn On. ...
  3. The Heater or AC Won't Turn Off. ...
  4. The Thermostat Reading Doesn't Match the Room Temperature. ...
  5. The Thermostat Doesn't Respond. ...
  6. The HVAC System Is Short Cycling. ...
  7. The Thermostat Forgets Programmed Settings.

Why is my outside AC unit not working but inside is?

Over time, the fan motor on the outside AC unit can wear out, causing the outdoor unit to stop working even when the inside AC unit is on. The fan motor can last 10 to 20 years with proper maintenance, like annual inspections and regular AC unit cleanings, but it will wear down faster without regular maintenance.

What is the first thing to check when the AC stops working?

Check these issues when the unit won't kick on: Check the thermostat and adjust the settings if it isn't set to Cool and an appropriate temperature setting to call for cooling. Examine the house circuit breakers for the AC unit and reset any tripped breakers. Check the air filter and replace the filter if it's dirty.

How do you reset the AC when it is not turning on?

2. Press the Reset Button
  1. Turn your thermostat to the “off” setting.
  2. Turn off the circuit breaker that powers your HVAC.
  3. Click and hold the reset button for three to five seconds.
  4. Restore power to your AC by flicking the circuit breaker back on.

What would cause your air conditioner not to come on?

The easy explanation for your AC not turning on is a thermostat issue. Double check your thermostat is on, set to “cool,” and that the temperature is set to a few degrees colder than the normal ambient temperature of your home. You may also need to replace the batteries.

How do I fix my AC not blowing air?

To fix an AC not blowing cool air, ensure the thermostat is set to "cool" mode and the temperature is set lower than the current room temperature. Inspect the air filter as a dirty filter can restrict airflow. Ensure the condenser coils are clean and free of debris. Make sure vents are open and unobstructed.

How do you reset an AC capacitor?

It's a small, red button usually located on or around the unit. The button should have a clear 'reset' label. Once you find the button, press it for around three seconds and observe the AC. Check whether the AC kicks on immediately and if it doesn't, press the button again for another three seconds.

What is the most common part to fail on an AC unit?

#1 Most Common Air Conditioning Repair – Bad Capacitor

The fan of course makes a whirring noise, the compressor is like a deep buzz like a refrigerator running. Holding your hand above the fan should feel warmer than the outside air.

How do you check if a capacitor is blown?

How to test a bad capacitor? Connect the multimeter probes to the capacitor and set it to capacitance mode. Then, take the value and compare it to the expected value of the capacitor. If it is within 10-20% it is good, if not, it is bad.

Why wont my outside AC unit kick on?

Look for a Tripped Breaker

If your AC won't turn on, you can check two places for a circuit breaker or electrical panel. Older homes have a main electrical panel on the outside of the home or a circuit panel on newer homes. Check the electrical panel to see if the breaker is tripped. Reset it if it is.

How much is a capacitor for an AC unit?

For AC capacitor replacement, anticipate spending between $150 and $400, depending on the capacitor's type and accessibility.

Why is my thermostat on but AC not running?

Check the power source and make sure it is connected and turned on. Verify that the circuit breaker for the AC unit is not tripped. Make sure the thermostat is set to 'COOL' mode. Check the fan setting on the thermostat and ensure it is set to 'AUTO' rather than 'ON'.

How much does it cost to replace a fuse in an AC unit?

AC Fuse, Circuit Breaker, or Relay Replacement Cost

Expect to pay between $15 and $300 to have AC fuse and circuit breaker issues addressed or relays in your AC unit replaced. These projects do not usually take more than a couple of hours.

Can a blown fuse cause my AC not to work?

Air conditioners can stop working if there is a blown fuse. Replacing that fuse can fix the problem, though it's important to have a certified car AC service technician check your electrical system.

Where are AC fuses located?

Where is the AC Fuse Located? The AC fuse on most HVAC systems is typically on the unit's control board. You'll normally find the board behind an access panel on the unit's lower compartment. While you sometimes have to unscrew areas to access the control board, others have clips.

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