Why Is My AC Running But Not Cooling?
If your air conditioner is not blowing cold air but running, the problem could be as simple as a dirty air filter or as serious as a leaking refrigerant line or a faulty component.
This guide breaks down the most common reasons why your air conditioner blows warm air, how to troubleshoot it, and when to call a professional.
If you’re in Las Cruces, NM, and tired of sweating through the day, contact Air Control Services at 575-567-2608. We offer 24-hour air conditioning repair service across the area and will help restore your cooling unit in no time.
Common Air Conditioner Cooling Problems
If your air conditioner is running but not cooling, it could be a thermostat issue, a clogged filter, a frozen coil, a refrigerant leak, a dirty condenser, a faulty compressor, electrical failure, or leaky ductwork.
Below are the most common cooling issues and how to spot them.
Inaccurate Thermostat Settings
If your thermostat is set to “On” instead of “Auto,” the fan keeps running whether or not the AC is actively cooling. That means you’ll get air blowing, but it won’t necessarily cool your home.
- Make sure the thermostat is set to Cool, not Heat
- Set the fan to Auto, not On
- Lower the temperature a few degrees below room temp and wait a few minutes
Dirty Air Filter
When your filter clogs up, the air can’t flow like it should. That causes two big problems: reduced cooling and potential freezing on the inside coil. Both can keep the indoor air warm, even when the AC is running.
If you notice weak air flow, turn off the AC system and check the filters. If it’s visibly dirty or gray, change it immediately. Since Las Cruces is a dusty city, we recommend changing the filters every 1 – 2 months.
Frozen Evaporator Coil
The indoor evaporator coil freezes when the airflow is restricted, either by a clogged filter, blocked vents, or a malfunctioning blower. It can also mean your system’s low on refrigerant.
Inspect your AC for:
- Ice on the indoor unit or refrigerant lines
- AC sounds like it’s working, but the room is warm
- Water pooling under the unit (when the ice melts)
If you notice any of these issues, turn off the system and switch the fan setting to “On”. This helps push warm air over the coil and speeds up the defrosting process. Don’t try to scrape the ice off as it can damage the coil.
Restart the system once the ice has completely melted (this may take a few hours). If it freezes up again, contact a licensed HVAC technician for air conditioning service.
Low Refrigerant or Leak
Your air conditioner relies on refrigerant to absorb heat from inside your home and release it outside. If the system is low on refrigerant or has a leak, your AC will run, but the room won’t feel cooler
However, this isn’t something that “runs out” over time. Low refrigerant always means there’s a leak somewhere in the system, whether it’s a loose connection, a damaged coil, or worn-out tubing.
Signs of a refrigerant issue:
- Hissing or bubbling sounds
- Ice on the evaporator coil or refrigerant lines
- Long cooling cycles
If you spot one or more of these issues, don’t keep running the system and avoid DIY fixes. Instead, call our local Las Cruces AC technician to find the leak, seal it properly, and recharge the system to the correct refrigerant level.
Dirty Condenser Coils
Condenser coils or the outdoor unit often get covered in dust, grass, or grime. This results in the AC running but not blowing cold air.
To clean the coils, turn off the power and rinse the coils gently with a garden hose – just enough to clear surface dirt. Avoid pressure washers, which can damage the delicate fins. Also, make sure the unit has at least two feet of space around it with no plants, fencing, or debris crowding it.
If cleaning doesn’t help or if the fins are bent, it may need a professional cleaning to restore performance.
Faulty Compressor
The compressor pumps refrigerant through the system, helping remove heat from your home. When it starts to fail, your AC may still run, but without cooling anything down.
Common warning signs of a faulty compressor include:
- Unit hums but doesn’t start
- Warm air from vents
- Frequent breaker trips
If the compressor has failed, it is often more cost-effective to replace the entire unit, especially if your system is older or already struggling with other problems. A trained HVAC technician can inspect the system and recommend the most suitable option for your AC.
Electrical Problems in the Air Conditioning System
Electrical problems, such as blown capacitors, faulty relays, or loose wiring, can prevent your AC from cooling properly. Even if the fan is blowing, your home may stay warm because the compressor isn’t getting the signal to turn on.
These electrical problems often show up as buzzing or clicking sounds, rapid on-off cycling (called short cycling), or frequent breaker trips. Sometimes, the unit sounds like it’s running normally, but no cool air is coming out.
If you suspect an electrical issue, turn off the system and avoid opening the access panels yourself. These components carry high voltage and can be dangerous without the right tools or training. A licensed HVAC contractor can safely test and replace faulty electrical parts to resolve the issue.
Leaky or Disconnected Ductwork
Leaky or disconnected ductwork can keep your AC from delivering cooling where you need it. Even if the system is working perfectly, holes or loose connections in the ducts can let conditioned air escape into the attic, crawlspace, or inside walls.
Signs of a leaky or disconnected ductwork include:
- Hot and cold spots throughout the house
- Dust buildup even with a clean filter
- Weak airflow from some vents
- Higher-than-normal cooling bills
A professional duct inspection can identify these leaks. Sealing and insulating the ductwork restores proper airflow and can significantly cut your energy use.
When to Call for AC Repair
If your basic checks, like adjusting the thermostat, replacing dirty filters, or clearing debris from the outdoor unit, don’t solve the problem of the air conditioner not blowing cold air, it’s time to call for professional AC repair. Issues like refrigerant leaks, faulty compressors, or frozen evaporator coils often need expert tools and training to fix.
Get Your Cold Air Back - Fast: Call Our HVAC Technician Today
Still wondering why your air conditioner is running but not cooling the house? You’ve changed the filter, double-checked the thermostat, and made sure the vents are open, but it’s still blowing warm air.
That’s your cue to call in a certified HVAC technician.
At Air Control Services, we’re ready 24/7 to diagnose the problem, make the fix, and get your cold air back – fast.
Call 575-567-2608 now!
Even musty odors can be harmful over time and trigger asthma, allergies, or respiratory problems, especially for kids and seniors.
If your AC smells strange and the stench doesn’t go away quickly, turn off the unit and have it inspected by a professional. Some issues are just unpleasant, but others are urgent safety hazards. When in doubt, play it safe and call a licensed HVAC technician near you for an inspection.
FAQs
Why is my split AC not cooling but the fan is running?
If your split AC is not cooling but the fan is running, the problem may lie in the condenser unit, low refrigerant, or a malfunction in the HVAC system. Clogged air filters or a sluggish blower fan can also reduce cooling, even though the system sounds like it’s working.
Why is it important to keep vents open?
Blocked or closed vents interrupt normal airflow, which causes uneven temperatures and forces the system to work harder. This can lead to uneven temperatures and strain on the equipment.
What does the blower fan do in an HVAC system?
The blower fan moves cooled or heated air through the ductwork and into your rooms. If it’s weak or not working, your space won’t reach the desired temperature.
How does insulation affect cooling and heating efficiency?
Poor insulation lets indoor temperatures escape, making your HVAC system work harder. Upgrading insulation helps maintain comfort and lower energy bills.