Central Air Conditioner Not Working? Learn Why
Key takeaways:
• The best way to find out why your home AC is not working is to call an HVAC professional.
• This article lists some possible causes, but a professional can say for sure and propose the fix.
• Don’t depend on ChatGPT for HVAC diagnostics.
By Anne Fonda
Whether you just turned your AC on for the first time or it’s been running hard for months, to suddenly find that your house feels like a sauna, or worse yet, a hot and humid tropical jungle, can be an uncomfortable shock.
Whether the AC is failing to turn on at all or is blowing hot air, you should plan on calling for AC repair. But, if you’re like most people, you turned to Google or ChatGPT to see why your air conditioner is not working, hoping that it’s a simple fix.
We’ve pulled together some common reasons, but again, if it’s not a simple fix (listed below), you’ll need an HVAC technician to troubleshoot, identify the problem or problems, and make the repairs.
Don’t depend on what ChatGPT or another chatbot said. AI has its place, but it cannot diagnose and fix your HVAC system.
Reason #1 for AC not working: Thermostat issues
This has a simple fix. Before you call for AC repair, check the thermostat settings. Make sure it’s set to Cool, and the fan is set to Auto. Make sure that the set temperature is below the actual indoor temperature. If the air conditioning doesn’t kick in, move on to reason #2.
Reason #2 for air conditioner not working: Clogged or dirty filter
A dirty or clogged HVAC filter can cause major problems (including a frozen evaporator coil) with your air conditioning system. Find your filter (usually located next to the furnace or in an interior wall or even in the ceiling) and replace it if it’s dirty. This could be a simple fix. Read our blog on HVAC air filter replacement for some tips.
Reason #3 for air conditioner not working: Bad capacitor
The AC capacitor is a small part with a big job. It sends an electrical jolt to start your air conditioner’s compressor and outdoor fan motor when the thermostat signals the need for cooling. Once the AC unit is running, the capacitor reduces its energy output but continues to supply a steady current of power to the motor until the cooling cycle finishes.
A bad capacitor can lead to the unit running but not cooling or not turning on at all.
Reason #4 for an AC unit not working: Electrical problems
If your air conditioner won’t start, stopped suddenly, or you have a tripped breaker, an electrical issue may be to blame. But the root of the problem may not be the electrical system at all. An HVAC technician will troubleshoot, diagnose, and fix the issue.
Reason #5 for AC not working: Frozen evaporator coil
If your AC is running but not cooling, a frozen evaporator coil could be to blame. Look for visible icing at the indoor evaporator coil or on the outdoor refrigerant lines. If you see icing, shut the system down so the coil can thaw. Call for HVAC repair.
Reason #6 for an air conditioner not working: Compressor problems
Your central AC unit’s compressor pumps and circulates refrigerant through the system, maintaining adequate pressure during the refrigeration cycle. If the unit keeps tripping the circuit breaker, won’t start, or is running but isn’t blowing cold air, a compressor issue could be to blame. An HVAC technician will troubleshoot and fix the problem.
If it’s a quick and relatively inexpensive repair, the HVAC technician can likely get your air conditioner up and running the same day. However, if the problem is a refrigerant leak (signaled by low refrigerant levels) or a bad compressor, the repair might take longer, especially if parts are not available or the source of the leak isn’t obvious.
Be prepared to make the repair or replacement decision
While repairs are possible for almost any problem, depending on the age of your system, the technician may give you a quote for repair and another for HVAC replacement. You will need to weigh the pros and cons of repairing your system vs replacing it. Check out our Repair or Replace Guide for some tips on making the decision.
If you decide to replace your system, get multiple quotes on multiple systems, and be sure to ask about HVAC financing, which can make affording a new system easier.
Consider signing up for an HVAC maintenance plan
You want your HVAC system to last as long as possible. The best way to do that is to keep up with regular maintenance. For you, that includes:
- Changing the filter regularly, every 30-90 days
- Keeping indoor supply registers and return air vents clear (don’t block with furniture or drapes)
- Keeping plant life and debris away from the outdoor unit
“Good maintenance is always the best way to extend the life of your system and have the highest level of overall reliability. Fixing small problems over time can prevent bigger issues later.”
-Mark Woodruff, Senior Product Manager, Air Conditioners
For the best system performance, you should also plan on scheduling professional maintenance visits. It can be cost-effective to sign an HVAC service contract, which can include twice-yearly visits to tune up your air conditioner in the spring before cooling season starts, and a furnace tune-up in the fall before heating season begins. Heat pump systems should get checked twice a year as well.
Many HVAC maintenance plans/service contracts include discounts on parts and priority service – meaning you go to the front of the line if something goes wrong with your system during the longest heatwave or coldest temperatures.
Opt into American Standard Diagnostics for peace of mind
If you have an American Standard smart thermostat, you can opt into remote monitoring and HVAC diagnostics. Once you have, your smart thermostat sends performance and system data to your American Standard dealer.
“With American Standard Diagnostics, your system is connected and designed to share performance insights with your dealer so they can spot, diagnose, and often fix issues remotely. That means fewer surprises for the Technician, faster service for the homeowner, and comfort that never takes a day off.”
-Marc Racine, Product Manager, Diagnostics and Tech App
This allows them to spot performance trends and receive alerts that might indicate a problem, sometimes before you notice a difference in your comfort level. Proactive HVAC maintenance and repair of small problems before they become big ones can save you money and help prolong the life of your system.
You can upgrade your current thermostat, whether you have an American Standard system or another brand.
Schedule AC repair
If your air conditioner is not working, don’t sweat it. Call your local American Standard dealer for help. Many dealers offer emergency AC repair, 24/7.
Anne Fonda, Content Writer
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 Mark Woodruff, Senior Product Manager, Air Conditioners
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