Quick Answer: The most common reasons your AC isn't blowing cold air are a dirty air filter, low refrigerant, or a frozen evaporator coil. Start by checking your thermostat settings and air filter — these are easy DIY fixes. If the problem persists, you likely need a professional to diagnose issues with refrigerant, the compressor, or electrical components. Most AC repairs cost between $150 and $600, depending on the issue.
We get it — sweating through it when your AC isn't working is miserable. All you want is the relief of cool air. Identifying the issue can help you know how to fix it or at least give the experts the necessary information to bring the right equipment.
Below, we walk through 13 of the most common reasons your air conditioner might not be cooling properly — starting with the issues you can check yourself, then moving to problems that typically require professional repair.
Issues You Can Check Yourself
Before calling a technician, check these common causes. Many homeowners can resolve these without professional help.
1. Clogged Air Filter
Air filters remove debris and other contaminants from the air before circulating it through the system. Dirty air filters force the system to work harder to create sufficient airflow, which can lower efficiency and performance. Clogged filters can also compromise the internal components of the system.
If you notice that your air conditioning is not blowing cold air, checking and replacing the air filter is the simplest place to start. Most filters cost $5–$20 and can be swapped in under five minutes.
DIY difficulty: Easy — no tools required
2. Incorrect Thermostat Settings
In order to provide cooling, your thermostat must be set to "auto" or "cool." If your thermostat shows "fan" or "heat," change it and see if that solves the problem. This is one of the most common issues homeowners encounter — and one of the easiest to fix on your own.
Also check that the set temperature is actually lower than the current room temperature. It sounds obvious, but it's worth confirming before moving on to more complex causes.
DIY difficulty: Easy — just check the settings
3. Thermostat Issues
Sometimes, the thermostat itself may have more complicated issues. Settings that seem correct but don't trigger cooling at the right time may indicate a problem with the sensor or the thermostat's connection to the system. Try replacing the batteries first. If that doesn't help, you may need to reach out to a professional.
DIY difficulty: Easy (battery swap) to Moderate (sensor/wiring issues)
4. Closed or Blocked Registers
Make sure to check the registers throughout your house to ensure they're open and unobstructed. Closed or blocked registers restrict airflow and can make one room feel much warmer than others. If the register appears open but airflow is still weak, you may have a blockage in the ductwork.
DIY difficulty: Easy — walk through each room and check
5. Tripping Circuit Breaker
A sudden power surge can trip the circuit breaker or blow a fuse, causing the air conditioning system to shut down. Power issues are the most likely cause of your air conditioner not turning on at all. If you notice the breaker needs resetting, reset it and try to turn the system on again. If the breaker trips repeatedly, that may indicate electrical issues in the system, such as faulty connections or a failing capacitor.
DIY difficulty: Easy (one-time reset) — but repeated tripping means call a pro
Causes That Typically Require Professional Repair
If you've checked the basics above and your AC still isn't cooling, one of these more complex issues is likely the cause. These typically require a licensed HVAC technician to diagnose and repair safely.
6. Low Refrigerant
Refrigerant is what cools the air coming from your AC. Air conditioning systems require refrigerant to extract heat from the indoor air. The closed refrigerant line keeps the system running throughout its lifespan, but leaks can lead to a low charge.
You can spot a leak by looking for dripping or listening for hissing sounds near the refrigerant lines. Because refrigerant contains toxic chemicals, you should call a licensed technician for repair. Do not attempt to handle refrigerant yourself.
Estimated repair cost: $200–$600 depending on the type of refrigerant and severity of the leak
7. Frozen or Dirty Evaporator Coil
The evaporator coil sits inside your air conditioning system, cycling refrigerant through the coil to absorb heat and humidity. If the evaporator coil gets dirty, it may stop working effectively. Excessive dirt and debris can lead to a frozen coil, which can cause the system to shut off too quickly, cycle room-temperature air, or break down entirely.
Related Post: How to De-Ice a Window Air Conditioner
Estimated repair cost: $150–$450 for cleaning; $600–$2,000+ if coil replacement is needed
8. Blocked Condenser Coil
The condenser coil helps release heat from the refrigerant so the cooling process can begin again. When your condenser coils get dirty, they make it harder for the system to eliminate heat. You may notice the system continues to operate, but cooling efficiency drops noticeably.
You can carefully brush off the exterior coils to clear grass clippings, dirt, and other debris. For a deeper clean, see our step-by-step guide in the FAQ section below.
DIY difficulty: Moderate (exterior cleaning) — internal cleaning requires a technician
9. Clogged Condensate Drain Line
Your air conditioning system releases humidity from the indoor air through a condensate drain line that leads out of your home. Like any other pipe, this drain line can accumulate dirt, algae, or ice. A significant blockage causes condensation to back up into the system, which can lead to short cycling or a complete shutdown.
Related Post: How To Stop And Prevent Your AC From Leaking Water
Estimated repair cost: $75–$250
10. Wrong System Size for Your Home
When you buy a new air conditioner, you need to choose an HVAC system that's the right size for your home. An undersized system will struggle to keep up with the cooling load, leading to poor performance, low efficiency, and accelerated wear and tear.
If your existing system cannot meet your needs even after repairs, you may want to consider a ductless mini-split installation for zoned cooling and higher efficiency.
11. Leaky Ductwork
If air is blowing from your vents but it's not cooling the house, the conditioned air may be escaping through leaks in the ductwork before it reaches certain rooms. This can make some rooms feel colder while others stay uncomfortably warm. A professional duct inspection can identify and seal leaks to improve performance and efficiency.
Estimated repair cost: $200–$700 depending on the extent of the leaks
12. Faulty Compressor
Your AC's compressor is a critical component that pressurizes refrigerant so the system can cool your home. If it's not working properly, you won't get the cooling you expect. Oil leaks or stains near your AC compressor are a sign you need to contact a professional for diagnosis.
Estimated repair cost: $400–$1,300 for repair; $1,500–$3,000+ for replacement
13. Broken Condenser Fan
There are several reasons the condenser fan might stop working — the fan capacitor, contactor, motor, or belt could all be the culprit. You can check your circuit breaker to make sure the AC unit is getting power, but beyond that, you'll need an expert to diagnose the specific issue. It's time to call the AC repair experts.
Estimated repair cost: $150–$700 depending on the component
When to Call a Professional vs. DIY
Not every AC issue requires a service call, but some problems are too dangerous or complex to handle on your own. Here's a quick guide:
Try It Yourself | Call a Professional |
|---|---|
Replace the air filter | Refrigerant leak or recharge |
Check and adjust thermostat settings | Frozen evaporator coil |
Open blocked registers | Compressor or fan motor issues |
Reset a tripped breaker (once) | Repeated breaker trips |
Clear debris from exterior condenser | Ductwork leaks |
Replace thermostat batteries | Any electrical component replacement |
Rule of thumb: If the fix involves refrigerant, electrical components, or opening up the system beyond basic filter access, call a licensed HVAC technician. Attempting complex repairs yourself can void your warranty, damage the system, or create safety hazards.
How Much Does AC Repair Cost?
AC repair costs vary depending on the issue, your location, and the age of your system. Here are typical ranges for the most common repairs:
Repair Type | Typical Cost Range |
|---|---|
Diagnostic service call | $75–$150 |
Condensate drain line clearing | $75–$250 |
Capacitor replacement | $150–$400 |
Evaporator coil cleaning | $150–$450 |
Refrigerant recharge | $200–$600 |
Fan motor replacement | $200–$700 |
Ductwork repair | $200–$700 |
Compressor repair | $400–$1,300 |
Compressor replacement | $1,500–$3,000+ |
Note: These are national average ranges and may vary by location. Schedule a service call with ARS/Rescue Rooter for an accurate estimate based on your specific situation.
Prevent AC Problems with Regular Maintenance
Most AC breakdowns are preventable. Scheduling annual HVAC maintenance helps keep your system clean and running efficiently, which can increase AC efficiency and reduce the chances of an unexpected breakdown during the hottest days of the year.
A professional tune-up typically includes cleaning coils, checking refrigerant levels, inspecting electrical connections, and testing system performance — addressing many of the issues above before they become problems.
Related Post: What to Expect During an HVAC Inspection
Call ARS/Rescue Rooter for Expert AC Repair
When your AC isn't blowing cold air and you've ruled out the simple fixes, it's time to turn to the experts at ARS/Rescue Rooter. Our licensed technicians can diagnose the issue quickly and get your system back to full cooling performance.
Frequently Asked Questions
What do I do if the AC is not blowing cold air?
Start with the basics: check your thermostat settings, replace the air filter, and make sure all registers are open. If those don't solve the issue, the problem is likely more complex — such as low refrigerant, a frozen coil, or an electrical issue. Call the experienced team at ARS/Rescue Rooter at 866-399-2885 for a professional diagnosis.
While you wait for service, here are some tips to help you stay cooler.
Should I turn off my AC if it's not cooling?
Yes, turn the system off if it's not cooling properly. Running a malfunctioning AC can cause further damage to components like the compressor. If the problem involves a refrigerant leak, continuing to run the system can worsen the leak and increase repair costs.
How do I reset my air conditioner?
Start by turning off the AC at the thermostat. Then look for a reset button on the exterior of your outdoor unit. If you can't find one, locate the HVAC circuit breaker in your electrical panel, flip it off, wait at least 60 seconds, then flip it back on. Wait 30 minutes before turning the AC back on at the thermostat to allow the system's internal pressure to equalize.
How much does it cost to fix an AC that's not blowing cold air?
Most AC repairs cost between $150 and $600, depending on the issue. Simple fixes like a capacitor replacement run $150–$400, while more complex repairs like a refrigerant recharge cost $200–$600. Compressor repairs or replacements can run $400–$3,000+. A diagnostic service call typically costs $75–$150, which is often applied toward the repair cost.
How long does it take for an AC to cool down a house?
A properly working AC system should begin cooling your home within 15–30 minutes. How quickly it reaches your desired temperature depends on the outside temperature, the size and efficiency of your system, the size of your home, and how well-insulated it is. If your AC runs for more than an hour without noticeable improvement, there's likely an underlying issue.
How do you fix an AC that is running but not cold?
An AC that runs but doesn't cool is usually caused by low refrigerant, a dirty evaporator coil, a blocked condenser, or leaky ductwork. Start by checking your air filter and thermostat. If those are fine, the fix will depend on the specific cause — and most of the remaining possibilities require a professional to diagnose safely.
How do you unclog a condenser coil?
You can clean the exterior of your condenser coil with these basic steps:
Turn off your AC — flip the breaker to be safe.
Remove the exterior covers from the unit (you'll need a screwdriver).
Clear any visible debris like leaves, twigs, and grass clippings.
Vacuum the fins using a brush attachment to remove accumulated dust.
Spray with AC coil cleaner (available at hardware stores). Let it sit 5–10 minutes.
Rinse with a garden hose — spray from the inside out to push debris away.
Let it air dry for a few minutes, then replace the covers and restore power.
For a deeper internal cleaning, call a professional — improper cleaning can damage the delicate coil fins.
