Outside AC Unit Not Turning On - Troubleshooting Guide


Outside AC Unit Not Turning On - Troubleshooting Guide

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If your outside AC unit is not turning on, it can be a significant inconvenience, particularly during those hot summer months. There are many potential reasons why your outside unit is not turning on - from minor issues like a tripped circuit breaker to more serious problems like a broken compressor. In this article, we are going to dive deep into the topic, helping you grasp the possible causes and solutions to your AC problem, and guide you towards the steps you can take to solve the issue.

Common Causes of an Outside AC Unit Not Turning On

Several factors could be contributing to your outside AC unit failing to start; some involve simple fixes, while others may require professional help. It's crucial to be familiar with some of these issues, so let’s take a look.

Electrical Issues

Often, electrical faults can lead to your outside AC unit not turning on. There could be a problem with your home circuit breaker or the disconnect switch on the outdoor unit itself.

  • A Tripped Circuit Breaker: This can result from power surges or overloads that might occur during a thunderstorm or due to an electrical issue with the unit.
  • A Blown Fuse: A blown fuse in the disconnect switch can prevent the outside AC unit from starting.

Thermostat Problems

Your thermostat controls when and how your air conditioning unit operates. If it’s set incorrectly or malfunctioning, your AC might fail to kick into action.

Faulty Capacitor or Contactor

The capacitor stores energy and delivers a boost to start the motor. Its partner, the contractor, is responsible for providing an electrical connection to start the compressor and the fan. If either of these components fail, they could be the culprit behind your outside AC unit not turning on.

Solving the Problem When Your Outside AC Unit Is Not Turning On

Now that you are aware of some common causes let's look at potential solutions.

Check Your Circuit Breaker and Fuses

Firstly, check your home's circuit breaker. If it has tripped, resetting it might fix the issue. Keep in mind that if your circuit breaker continually trips, it could be a sign of a bigger problem that a professional needs to address.

If your circuit breaker is fine, inspect the fuses in your outside unit's disconnect switch. Only replace a blown fuse if you have adequate knowledge of electrical systems; otherwise, engaging a professional is recommended to avoid personal injury.

Inspect Your Thermostat

Make sure your thermostat is set to "cool" and lower than the current room temperature. If your thermostat is non-responsive or shows a blank display, batteries might be the issue, and replacing them could solve your problem.

Consult a Professional

If you've checked the possible causes discussed above and your outside AC unit is still not turning on, it's time to call an HVAC professional. It's likely that the problem lies with internal components such as the capacitor or contractor, and these repairs should always be left to the experts.

Maintenance to Prevent Your Outside AC Unit From Not Turning On

Preventative maintenance plays a key part in preventing issues with your AC unit. With a regular maintenance routine in place, you can extend the lifespan of your unit and save money on costly repairs.

Regular Professional Maintenance

Scheduling regular professional checks can detect potential problems early, saving hefty repair costs in the long run. A professional technician will check all components of your unit, ensuring it operates correctly and efficiently.

DIY Maintenance

While professional checks are crucial, you can also perform some basic maintenance tasks yourself:

  • Clean or replace your air filters every month.
  • Keep the area surrounding your outside unit clear of dirt, leaves, and debris.
  • Check your thermostat batteries regularly.

If your outside AC unit isn't turning on, it can be stressful. However, by understanding the common causes and solutions, you can determine whether it’s a simple fix or if a professional technician needs to intervene.

Frequently Asked Questions About Outside AC Unit Not Turning On

Why isn't my outdoor AC unit working?

The outdoor AC unit may not be working due to several reasons. This might include electrical issues, issues with the thermostat settings, a dirty or clogged filter, refrigerant leakage, or a faulty motor. You should have it inspected by an HVAC professional to identify the cause and fix the problem.

What should I check if my outdoor AC unit is not turning on?

First, check your thermostat settings and ensure it's set on "cool" mode. Then, check your circuit breaker or fuse box to ensure power is being delivered to your outside AC unit. You should also inspect the outdoor unit for any signs of physical damage or debris that could be blocking airflow.

Could a bad thermostat cause the outdoor AC unit not to turn on?

Yes, a bad or incorrectly adjusted thermostat could indeed prevent the outside AC unit from turning on. If the device doesn't signal the air conditioning system to start, it won't activate. Check your thermostat’s settings and batteries if it’s not hardwired.

Could a dirty filter be the cause of an outside AC unit not turning on?

A dirty or clogged filter could indeed lead to the AC system functioning improperly or not at all. When the filter is clogged, airflow is restricted, which can cause the system to shut down to prevent overheating. Therefore, keeping filters clean should be a part of regular maintenance.

What happens when the outside AC unit doesn't turn on?

When the outside AC unit doesn't turn on, it means the cooling process isn't initiated. Without the outside unit operating, the system can't pull heat away from the home, which can result in a hot, uncomfortable environment indoors as well as increased energy bills.

Could the issue be a tripped breaker or blown fuse?

Yes, a tripped circuit breaker or a blown fuse could be the reason your outside AC unit isn't turning on because they interrupt power supply. Check the circuit breaker and electrical panel; if the breaker linked to the AC system is in the "off" position or if a fuse is blown, it will need to be reset or replaced.

How can I fix the issue of my outside AC unit not turning on?

First, identify the possible issues, such as a tripped circuit breaker, a blown fuse, a bad thermostat, or a dirty filter. After identifying and resolving the issue, if the unit still doesn't turn on, you may need to contact a professional to diagnose it for a potential deeper problem such as a faulty motor or refrigerant leakage.

Can regular maintenance prevent an outside AC unit from not turning on?

Yes, regular maintenance can prevent many issues that might cause your outside AC unit not to turn on. Routine maintenance should include cleaning or replacing the air filter, checking wiring and connections, cleaning the outdoor unit, and inspecting the condensate drain. Scheduling an annual professional inspection would also be helpful.

Should I call a professional if my outside AC unit is not turning on?

Yes, if you've tried troubleshooting the basic issues and your outside AC unit still doesn't turn on, you should call a professional. An HVAC specialist has the knowledge and equipment needed to safely diagnose and fix the problem.


There could be numerous reasons why your outside ac unit is not turning on, ranging from electrical issues to faulty parts. Always begin with checking the basics, like power supply and thermostat settings. Then you can move onto more complex troubleshooting. Take note, it's important to remember that regular maintenance can oftentimes prevent such issues from happening.

If your outside AC unit is not turning on still after your initial troubleshooting efforts, it might be time to bring in the experts. Particularly, if you suspect there's a problem with the circuit board or the motor, you should definitely let a professional take a look. Working with these types of components can be dangerous if not handled correctly.

Lastly, remember to stay cool and don't panic if your outside AC unit not turning on phenomenon occurs. In many cases, the issue turns out to be a simple fix that homeowners can handle themselves. But, even when it's not, there are professionals who can handle the job and ensure your AC is back up and running in no time.

About Perfect Air & Water Services

Welcome to Perfect Air & Water Services, Lakewood's trusted provider of high-quality HVAC solutions. Fiercely local and passionately dedicated to the comfort of our community, we've been ensuring your homes stay cozy and your businesses run smoothly since our inception. With a commitment to top-notch workmanship and incomparable customer service, we specialize in all matters of air conditioning, heating, and water purification. When it comes to maintaining perfect temperature and crystal clear water, we never leave room for compromise. Switch to Perfect Air & Water Services and experience the difference firsthand!