If you are wondering why your AC is not blowing cold, the answer is often one of a few common problems, thermostat settings, restricted airflow, dirty coils, refrigerant issues, electrical problems, damaged ductwork, or failed components. Knowing these warning signs can help you check simple items yourself and give a service technician better information for a faster diagnosis.
Air conditioning has become an essential part of daily life, and losing cool air can quickly make your home uncomfortable. Some causes are easy to spot, while others require a professional inspection. The list below covers 8 common reasons an air conditioner may stop blowing cold air, while keeping the original facts and guidance intact.
Why your AC is not blowing cold, what should you check first?
Start with the simplest items before assuming the worst. In many cases, the issue is visible or easy to test safely without tools.
- Check that the thermostat is set to cool
- Make sure the temperature is turned down low enough for the unit to run
- Confirm the fan is set to auto, not on
- Look at the air filter for dirt and blockage
- Check whether the outdoor unit is running
- Inspect for ice forming on copper lines
- Look at the breaker panel if the indoor blower runs but the outdoor unit does not
If these steps do not solve the problem, the system may need professional service. The Right Choice Texas can help homeowners narrow down whether the issue is airflow related, electrical, refrigerant related, or mechanical.
Could the thermostat be why your AC is not blowing cold?
It is easy to overlook the thermostat, especially now that many homes have smart thermostats. A simple setting mistake can make it seem like the system is not cooling when it is actually operating based on the wrong command.
Check that the thermostat is set to cooling mode and that the temperature is low enough for the air conditioner to start. Also make sure the fan is not set to on. If the fan is set to on, it runs constantly and may lead you to believe the air conditioner is not working because air is still moving even when the system is not actively cooling.
Is a dirty air filter stopping cold airflow?
All too often, the problem comes down to a dirty filter. Your air conditioner must have air moving through the return and across the coil to work correctly. If the filter is clogged and does not allow air to move through it, it can cause severe issues.
One important sign is ice forming on the copper lines at the indoor unit or on the copper lines at the outdoor unit. When airflow is restricted, the system can begin to freeze. That makes a dirty filter one of the first things to check when asking why your AC is not blowing cold.
For more ways to reduce strain on your system, see Home Energy Savings Tips.
Can a dirty indoor coil cause your AC to stop cooling?
A dirty indoor coil can cause the air conditioner to react very similarly to a dirty air filter. This is generally caused by running the unit without a filter. Once the coil gets overly dirty, air cannot pass through it efficiently and it will begin to freeze.
This is generally something you will want a professional to clean. The aluminum fins that make up the coil are fragile, and cleaning them incorrectly can cause problems. If you suspect heavy indoor coil buildup, schedule service instead of trying to force a cleaning.
Is the outdoor coil too dirty to release heat properly?
Outdoor coils are notorious for getting dirty. As the outdoor unit runs, it pulls air through the outside of the unit and pushes it out the top. Grass clippings can get pulled into the coil during mowing, and loose leaves, pollen, and pet hair can build up over time.
Like the indoor coil, the system needs air to pass through this coil to work correctly. However, the outdoor coil is something a homeowner is generally capable of cleaning, and it is even recommended. Take a garden hose and spray through the coil, working up and down around the coil. Doing this regularly will significantly help the unit’s ability to operate. If the unit has become excessively dirty, a technician may still need to clean it properly.
If you want a professional maintenance reference, see Air conditioning TuneUp Checklist, What We Do During Your Annual Clean.
Could refrigerant be why your AC is not blowing cold?
Most people assume refrigerant is the problem when the air conditioner is not working. But refrigerant is not to blame a fair amount of the time. It should be diagnosed by a service technician using a set of gauges.
Your service technician should check refrigerant to proper superheat and subcooling levels to assure that refrigerant is at the proper levels. Because this is a technical measurement and handling refrigerant requires training, this is not a do it yourself task.
If your system uses older refrigerant, you may also want to read Will You Need To Replace You Freon-Based Air Conditioners by 2020.
Is there no electricity going to the outdoor unit?
If the outdoor unit is not running, it may not have any electricity. This is another issue you may have a chance of fixing yourself. If your blower motor is running and blowing air into your home, but the outdoor unit is not running, check the breaker panel.
If there is a breaker labeled A/C or air conditioner, make sure it is turned on. If there is not, check whether any double pole breaker, what looks like 2 breakers tied together, has tripped. Sometimes a breaker shows it has tripped by displaying an orange strip. Sometimes the handle is stuck in the middle between the on and off positions.
In that case, you can step to the side of the panel, reach across, turn the breaker off, and then flip it back on. If it trips again, you will need to call a professional service technician.
Could damaged ductwork be the reason you are not getting cold air?
There are times when critters get into homes, and when that happens they can cause problems with ductwork. Whether the ductwork is in the attic or crawl space, a raccoon or even a stray cat may gain access and cause damage.
If you have entirely metal duct, severe damage is less likely, though animals may still tear up insulation and reduce efficiency. The real problems often happen with flexible ducting. Flexible ducting is similar to an adjustable dryer vent wrapped in insulation. If an animal chews a hole in it, the problem can quickly worsen. You could have half of the supply runs throughout the home destroyed before you know what has happened.
Are mechanical issues more common than refrigerant problems?
Although homeowners often suspect refrigerant first, there are far more mechanical issues than refrigerant problems. Capacitors are a common failure. When they go out, a common symptom is that the indoor unit runs but the outdoor unit does not.
Fan motors can also fail. In that case, the outdoor unit may sound like it is running, but the condenser fan on top is not spinning, and the unit may be humming loudly. These are clear signs that the system needs professional diagnosis.
What if the compressor has failed?
One of the worst problems is a failed compressor. This is the heart and soul of the air conditioning system. The black cylinder in the bottom of the outdoor unit pumps the freon in between the units.
Compressors are costly to replace. Depending on what caused the failure, you may now have acid in the system that will have to be neutralized, and you will have to have all new refrigerants installed. That means you may face a hefty bill if you intend to have it fixed.
What are the 8 common reasons your AC is not blowing cold?
| Problem | What to check | Can you check it yourself? |
|---|---|---|
| Thermostat | Cooling mode, temperature setting, fan on auto | Yes |
| Air filter | Dirt, blockage, ice on copper lines | Yes |
| Dirty indoor coil | Restricted airflow, freezing | Usually no |
| Dirty outdoor coil | Grass clippings, leaves, pollen, pet hair | Yes |
| Refrigerant | Proper superheat and subcooling levels | No |
| No electricity | Breaker condition, outdoor unit power | Yes |
| Ductwork issue | Animal damage, torn flexible duct, missing insulation | Sometimes |
| Mechanical issues | Capacitor, fan motor, compressor symptoms | No |
When should you call an HVAC professional?
You should call for service if the breaker keeps tripping, the system is icing up, the outdoor unit will not run, or you suspect refrigerant or mechanical failure. Those problems usually require tools, testing, and repair experience that go beyond basic homeowner troubleshooting.
If you need help determining why your AC is not blowing cold, contact a trusted heating and air conditioning service company. The Right Choice Texas can inspect the system, identify the cause, and recommend the right next step based on the actual condition of the equipment.
Frequently asked questions about why your AC is not blowing cold
Can a thermostat setting really make it seem like the AC is broken?
Yes. If the thermostat is not set to cool, the temperature is not set low enough, or the fan is set to on instead of auto, it may seem like the system is not cooling properly.
What is the first physical part I should inspect?
The air filter is one of the first things to inspect. A dirty filter can restrict airflow, cause severe issues, and even lead to ice forming on copper lines.
Can I clean the outdoor coil myself?
Yes. It is even recommended. You can use a garden hose and spray through the coil, working up and down around it. If the buildup is excessive, a technician may still need to clean it properly.
Should I assume low refrigerant is the problem?
No. Refrigerant is not to blame a fair amount of the time. A technician should check refrigerant using gauges and verify proper superheat and subcooling levels.
What if the indoor unit runs but the outdoor unit does not?
Check the breaker panel first. If the breaker has tripped, reset it once. If it trips again, call a professional service technician.
Can animals damage ductwork enough to affect cooling?
Yes. This is especially true with flexible ducting. Animals can chew holes into it, and multiple supply runs may be damaged before the issue is discovered.
Why are mechanical issues such a concern?
Mechanical issues are common and can involve the capacitor, fan motor, or compressor. A failed compressor is one of the most serious and costly air conditioning problems.