When we turn on the AC after a year, it stops cooling.The main reasons for the AC not cooling are: Dirty air filter, blocked vents and outdoor unit, frozen operator coil, faulty capacitor and compressor. All these reasons stop the AC from cooling, due to which we do not get to see the same results as before.
Check thermostat settings (set to “Cool”), replace dirty air filters, and clear blocked vents/outdoor unit. If frozen coils or low refrigerant persist, thaw coils or call an EPA-certified technician for leaks. For humming units or no cool air, capacitor/compressor repairs may be needed.
Reasons why AC stop cooling:
- Thermostat Settings
- Dirty Air Filter
- Blocked Vents or Outdoor Unit
- Frozen Evaporator Coils
- Faulty Capacitor or Compressor
1.Thermostat Settings:
Your thermostat controls your AC’s operation. Incorrect settings (e.g., “Fan” mode instead of “Cool”) or placement near heat sources can trick it into blowing warm air or running nonstop, wasting energy and straining the system.
What Is a Thermostat?
A thermostat is your AC’s “brain”—it senses room temperature and signals your system to start/stop cooling.
Quick Fixes
- Check Mode: Ensure it’s set to “Cool” (not “Heat” or “Fan Only”).
- Adjust Temperature: Set it 5°F below current room temp (e.g., 73°F if it’s 78°F).
- Battery Check: Dead batteries in wireless units cause glitches—replace yearly.
Avoid Common Mistakes
- Don’t place thermostats near windows, lamps, or vents—heat/cold drafts trick sensors.
- Old dial models often lose calibration. Upgrade to a smart thermostat (e.g., Nest) for precise control.
When to Call a Pro
If settings are correct but your AC still blows warm air, faulty wiring or a broken sensor likely requires a licensed technician’s expertise.
AC Not Cooling 2.Dirty Air Filter: The Silent AC Killer (Fix It Now!)
A dirty air filter is the #1 cause of ACs running but not cooling. Clogged filters block airflow, forcing your system to overwork—leading to frozen coils, higher energy bills, and premature breakdowns.
How to Fix It
- Locate the Filter: Check behind return vents, in the indoor unit, or attic (refer to your AC manual).
- Inspect for Dirt: Hold it up to light. If it’s gray and opaque, replace it immediately.
- Choose the Right Filter: Use MERV 8-11 pleated filters—they trap dust without restricting airflow. Avoid cheap fiberglass filters (they’re less effective).
Why It Matters
Neglecting filters reduces cooling power by 15% and strains critical parts like the blower motor. Replace filters every 1-3 months, especially with pets or allergies.
When to Call a Pro
If airflow stays weak after replacement, hidden issues like duct leaks or failing components may need expert diagnosis.
Pro tip:Replace filters every 1-3 months
AC Not Cooling 3.Blocked Vents or Outdoor Unit:
If your AC isn’t cooling, blocked vents or a clogged outdoor unit could be to blame. Restricted airflow forces your system to strain, wasting energy and risking damage.
Indoor Fixes (2 Minutes)
- Unblock Vents: Move furniture, rugs, or decor covering vents.
- Check Return Vents: These large vents (often on walls) pull air into the system—keep them dust-free and open.
Outdoor Fixes (5 Minutes)
- Clear Debris: Remove leaves, dirt, or plants within 2 feet of the outdoor unit.
- Trim Plants: Cut back bushes or branches blocking airflow.
Why This Matters
Blocked airflow can spike energy bills by 15% and freeze coils.
Pro Tip: Turn off power, then gently rinse the outdoor unit with a hose to clear dirt.
Still No Luck?
Persistent issues may signal duct leaks or refrigerant problems—call a licensed technician.
4.Frozen Evaporator Coils:
These are the icy metal coils inside your AC’s indoor unit. Ice blocks airflow, making your AC blow warm air or stop cooling.
Why It Happens
- Dirty air filters or blocked vents restrict airflow.
- Low refrigerant levels (a leak).
- Broken blower fan.
Fix It Fast
- Turn Off AC: Let coils thaw for 3-5 hours.
- Replace Filter: Use MERV 8-11 to improve airflow.
- Check Vents: Ensure none are blocked by furniture.
When to Call a Pro
If ice returns after thawing, you likely have a refrigerant leak or electrical issue—only certified technicians can safely handle Freon or repair components.
Prevention
Clean filters monthly and keep vents clear.
AC Not Cooling 5.Faulty Capacitor or Compressor:
A failing capacitor (starts the compressor) or compressor (pumps refrigerant) can leave your AC blowing warm air.
Signs to Watch
- Humming noise from the outdoor unit.
- AC won’t start or shuts off quickly.
- Intermittent cooling.
DIY Checks (Safety First!)
- Turn off power at the breaker.
- Inspect the capacitor: Bulging or leaking means it’s bad.
- Test with a multimeter (if skilled)—replace if readings don’t match the label.
When to Call a Pro
- Capacitor replacement: $150–$400.
- Compressor repair/replacement: $1,000–$2,500+.
Prevention: Annual maintenance catches early wear.
metal coils inside your AC’s indoor unit. Ice blocks airflow, making your AC blow warm air or stop cooling.
Why It Happens
- Dirty air filters or blocked vents restrict airflow.
- Low refrigerant levels (a leak).
- Broken blower fan.
Fix It Fast
- Turn Off AC: Let coils thaw for 3-5 hours.
- Replace Filter: Use MERV 8-11 to improve airflow.
- Check Vents: Ensure none are blocked by furniture.
When to Call a Pro
If ice returns after thawing, you likely have a refrigerant leak or electrical issue—only certified technicians can safely handle Freon or repair components.
Prevention
Clean filters monthly and keep vents clear.
AC Not Cooling AC Not Cooling
When to Call a Pro
Issue DIY? Pro Cost Estimate Refrigerant leak ❌ $200–$500 Compressor replacement ❌ $900–$2,500 Electrical repairs ❌ $150–$600 Prevent Future AC Problems: 3 Easy Steps
- Monthly Filter Checks: Replace dirty filters (MERV 8-11) to avoid airflow blockages and frozen coils.
- Seasonal Outdoor Care: Clear leaves/debris around the outdoor unit and trim plants for 2-foot clearance.
- Annual Pro Tune-Up: Schedule a licensed technician to inspect refrigerant levels, clean coils, and test electrical components.
FAQ:
- Why is my AC running but not cooling?
A dirty or clogged air filter, low refrigerant from a leak, a faulty capacitor/compressor, or a broken thermistor can let the fan run while no cold air is produced. - How to fix AC not blowing cold air?
Start with DIY: replace a dirty filter, ensure thermostat is set to “Cool,” and clear debris around the outdoor unit. If it still blows warm air, you may need a refrigerant recharge or a capacitor swap by an HVAC pro. - How to fix AC cooling problem?
Follow a three-step check: (1) Verify thermostat settings and reset if needed, (2) inspect and clean filters/coils, (3) examine for ice on coils or hissing leaks—call a technician if issues persist. - How to clean blocked or clogged condenser coil?
Turn off power, remove the protective grille, use a soft brush or fin comb to clear debris, then spray a no-rinse coil cleaner. Let it sit per instructions, rinse with a gentle stream of water, and restore power.
- Why is my AC running but not cooling?
