Central AC Compressor Not Turning On

If your AC compressor is not turning on and the temperature in your house is rising, you’re desperate for solutions. We’re here to help. Be advised that you should plan on calling an HVAC professional for help. We don’t advise any homeowner to try and repair a malfunctioning compressor themselves.

The AC compressor plays a critical role in the refrigeration cycle that allows your AC system to send cool air throughout your home. The compressor pressurizes and circulates refrigerant through your HVAC system. Without it, there is no cooling.

There are several common causes for the outside AC unit compressor not to turn on. Let’s take a look at the causes and what you should do in each case.

This may seem silly but check to make sure the thermostat is set to COOL and the set temperature is lower than the current indoor temperature. Someone who got cold may have changed the air conditioning settings.

Your AC may not be working because there is no power to the compressor. Check your circuit breaker box to see if a breaker is flipped. If it is, consult with an HVAC professional. The breaker tripped due to an issue with your AC unit. Flipping the circuit breaker back on without figuring out why it tripped could damage your system.

Your air conditioner needs a lot of power to start up, which is why it has an AC capacitor. A start capacitor sends a jolt of electricity to the unit when the thermostat calls for cooling. A bad capacitor can cause the unit to be unable to start. An HVAC professional can diagnose the problem and replace the capacitor.

If the wiring connections inside your central AC unit are loose, they can prevent the compressor from starting up. Only a trained HVAC technician should touch the wiring on your unit. This is for your safety as well as to not void your warranty.

Your outdoor AC unit has two motors – the condenser fan motor and the compressor motor. The compressor motor will generally last the life of the system with proper maintenance. However, years of wear and tear can lead to a complete breakdown. Only an HVAC professional can determine this.

AC repair costs are a consideration. If it’s just a matter of tightening some loose connections or replacing a capacitor, most homeowners can easily handle that expense. However, if your compressor has died, you need to consider whether AC repair or replacement is a more cost-effective solution. Check out our Repair or Replace Guide for some tips.

You can help keep your AC running at peak performance with regular maintenance. Some you can do yourself and other work should be left to an HVAC professional.

Change the AC filter every 30-90 days based on the quality of the filter. Your thermostat may alert you to when you should change the filter. Otherwise, set a calendar alert on your phone. Something as simple as a clogged or dirty air filter can cause some big problems. See our HVAC filter maintenance guide for tips.

Keep the floor around the indoor unit clean and sweep away dirt, dust, and cobwebs. Keep landscaping at least two feet away from the outdoor unit to promote air circulation.

Schedule an AC tune-up every spring for optimal performance. The HVAC technician will do a full inspection and may catch problems while they are still small and before they lead to hefty AC repair costs. Sign up for their HVAC service plan and they will reach out to schedule appointments each spring and fall.

Finally, consider opting into Trane Diagnostics. This allows your Trane dealer to monitor your HVAC system remotely. They’ll receive alerts of any issues with your system and can act quickly to help you, even when you’re away from home on vacation.

Anne Fonda, Content Writer at Trane Technologies

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Kimberly Sexton, Senior Systems Engineer

How Long Do Air Conditioners Last?

AC Not Blowing Cold Air

AC Not Turning On

AC Short Cycling

Air Conditioner Leaking Water

Air Conditioner Smells Musty

How to Clean Condenser Coils

Evaporator Coil Is Frozen

How to Clean Evaporator Coils