Why Your AC Unit Won’t Start: Troubleshooting Guide for When It Won’t Turn On

Ever found yourself sweating buckets in your own home, wondering, “Why on earth is my AC unit not turning on?” You’re not alone. Picture this: it’s scorching outside, and your trusty air conditioner decides to take an unexpected vacation. Frustrating, right? But fear not, because in this article, you’ll uncover the secrets behind your AC’s silent treatment and learn how to bring back the cool breeze into your life. Stay tuned to discover the simple fixes that could save you from a hot mess and have you chilling in no time.

Check the Thermostat

When your AC unit is not turning on, the thermostat could be the culprit. Here’s what you can do:

  • Check the settings: Ensure the thermostat is set to cooling and the temperature is lower than the current room temperature.
  • Replace batteries: If your thermostat uses batteries, they might need replacing. It’s a simple fix that could get your AC up and running again.
  • Inspect for dirt or debris: Clean any dirt or debris around the thermostat that could be affecting its performance.
  • Try resetting: Sometimes a quick reset of the thermostat can solve the issue. Look for a reset button or switch and give it a try.

Can’t figure out why your AC isn’t turning on? Let’s move on to the next possible solution.

Inspect the Circuit Breaker

When your AC unit is not turning on, one common culprit could be a tripped circuit breaker. Here’s what you should do:

  • Go to your electrical panel and locate the breaker labeled “AC” or “HVAC.”
  • Check if the breaker is in the “ON” position.
  • If it’s in the “OFF” position, flip it to “ON.”

Click here to preview your posts with PRO themes ››

  • Look for any burnt or charred areas around the circuit breaker, indicating a potential problem.
  • If the breaker trips repeatedly, it could be a sign of a more serious issue, and you should contact a professional to diagnose and fix the problem.

Remember, proper maintenance of your electrical system is crucial for the longevity of your AC unit.

Examine the Air Filter

When your AC unit isn’t turning on, a clogged air filter could be the culprit. Over time, dirt and debris build up in the filter, restricting airflow and causing your AC to struggle.

To examine the air filter:

  • Locate the filter panel on your system.
  • Slide the filter out and hold it up to the light.
  • If you can’t see light through it, it’s time to replace it.

Regularly changing your air filter every 1-3 months can improve your AC’s efficiency and lifespan.

Look at the Capacitor

If your AC unit is still not turning on after checking the thermostat and breaker, it might be time to inspect the capacitor. The capacitor is crucial for starting the compressor and fan motors in your air conditioner.

Signs of a Faulty Capacitor

  • AC making humming noise but not starting
  • AC not cooling efficiently
  • AC constantly turning off and on

Checking the Capacitor

  1. Turn off power: Before inspecting the capacitor, ensure the power to your AC unit is off.
  2. Locate the capacitor: It’s typically a cylindrical device with wires connected to it.
  3. Check for bulging or leaking: A faulty capacitor may show physical signs of damage.
  4. Use a multimeter: If comfortable, test the capacitor with a multimeter for an accurate reading.

Click here to preview your posts with PRO themes ››

Important Note: Capacitors store electricity even when the power is off. For safety, consider contacting a professional if you’re unsure about handling electrical components.

Remember, a malfunctioning capacitor can prevent your AC unit from turning on properly. If you suspect an issue, it’s best to address it promptly to avoid further damage.


Ensuring your AC unit functions properly is vital for a comfortable home environment. If your AC isn’t turning on, checking the capacitor is crucial. Signs of a faulty capacitor can include strange noises and inefficient cooling. Remember to handle capacitors with care and seek professional help if needed. Addressing capacitor issues promptly can prevent further damage and keep your AC running smoothly. Stay proactive in maintaining your unit to enjoy cool and refreshing air during hot days.

Frequently Asked Questions

What should I do if my AC unit still doesn’t turn on after checking the thermostat and circuit breaker?

If your AC unit still doesn’t turn on after checking the thermostat and circuit breaker, it’s recommended to inspect the capacitor.

How do I know if the capacitor is faulty?

Signs of a faulty capacitor include a humming noise coming from the AC, inefficient cooling, and the unit frequently turning on and off.

How can I check the capacitor?

To check the capacitor, ensure the power is off, locate the cylindrical device with wires, inspect for physical damage like bulging or leaking, and consider using a multimeter for testing.

Why is it crucial to handle capacitors with caution?

Capacitors store electricity even when the power is off, so it’s essential to handle them with caution to avoid electrical accidents.

Click here to preview your posts with PRO themes ››

Should I seek professional help for capacitor issues?

Yes, it’s recommended to seek professional assistance if you are unsure about handling capacitor issues due to the potential risks involved.

Why is addressing capacitor issues promptly important?

Addressing capacitor issues promptly is crucial to prevent further damage to your AC unit and ensure it functions properly.

Charlie Thomson is Appliance Mastery's expert on laundry appliances. With a degree in mechanical engineering and over 8 years of experience in the appliance repair industry, Charlie is a go-to resource for homeowners who want to tackle common issues with their washing machines, dryers, and dishwashers.

Leave a Comment

Send this to a friend