Kennesaw, GA AC Repair: 7 Reasons Your AC Isn’t Cooling

Estimated Read Time: 8 minutes

AC running but not cooling? You are not alone in Atlanta’s heat and humidity. When the blower is on but the air feels warm or weak, you need fast diagnosis and a fix that lasts. Our same‑day AC repair team combines rigorous testing with upfront recommendations so you know exactly what it costs and why it happened. Keep reading for seven common causes, what to check, and when to call for help.

1) A dirty or clogged air filter is choking airflow

A starved AC cannot move enough air across the evaporator coil to absorb heat. In Atlanta, pollen spikes and red clay dust clog filters faster than homeowners expect. When airflow drops, your system may run constantly, deliver lukewarm air, and even short‑cycle.

What you can do now:

1. Inspect your filter for gray matting or debris. Replace 1‑inch filters every 30 to 60 days during summer.
2. Make sure the arrow on the filter frame points toward the blower.
3. Open supply registers fully and clear furniture from return grilles.

What our techs check:

1. Static pressure and temperature drop across the coil.
2. Blower speed, amperage, and wheel cleanliness.
3. Duct restrictions that mimic a dirty filter problem.

If your filter is clean but airflow is still weak, move to the next likely causes below.

2) Low refrigerant or a refrigerant leak

Your AC cools by evaporating refrigerant inside the indoor coil and rejecting heat outdoors. Low charge means the coil cannot absorb enough heat, which produces warm air and long run times. You might also see icing on the refrigerant lines or hear a faint hissing.

What you can check safely:

1. Look for ice on the copper lines or at the air handler. If you see frost, turn the system off and run the fan only to thaw.
2. Note any recent spikes in energy bills or rooms that never cool.

Our diagnostic approach:

1. Measure superheat and subcool to manufacturer specs, not guesswork.
2. Perform leak detection before adding refrigerant. Topping off without finding the leak is a temporary bandage.
3. Present clear options: pinpoint repair, component replacement, or system replacement if age and parts availability make more sense.

Hard fact: Adding refrigerant without repairing a confirmed leak violates best practice and risks environmental harm. Our licensed team follows EPA handling standards and documents the fix.

3) A frozen evaporator coil

A coil can freeze from low airflow, low refrigerant, a stuck expansion device, or a failed blower. Ice insulates the coil, so the air feels warm even while the unit keeps running.

Immediate steps:

1. Turn cooling off. Set the thermostat to Fan On for 60 to 90 minutes to thaw the coil.
2. Replace a dirty filter and open closed vents.
3. Check that the evaporator drain is not clogged. A backed‑up drain can trip a float switch and shut cooling while the fan still runs.

What we inspect:

1. Expansion valve performance and temperature across the coil.
2. Start and run capacitors for the blower motor.
3. Drain pan, trap, and safety switches.

From our maintenance checklist: we verify temperature drop, check the expansion valve, clean or clear the evaporator drain if needed, and confirm blower operation. Preventive care here prevents repeat freeze‑ups during peak heat.

4) Weak capacitors or a failing compressor fan

If your indoor fan runs but cooling is poor, the outdoor unit may not be rejecting heat well. Common culprits are a swollen start or run capacitor, a failing condenser fan motor, or a compressor that is struggling under high ambient temperatures.

Symptoms you may notice:

1. Outdoor unit humming but not spinning, or starts then stalls.
2. Breaker trips when cooling calls start.
3. Hot air from vents and a very hot top fan grille outside.

Our procedure:

1. Test start and run capacitors under load. Replace any out‑of‑spec part with matched components.
2. Verify condenser fan motor amperage and rotation.
3. Check coil cleanliness and temperature across condenser coils to ensure proper heat rejection.

Good news: Many no‑cool conditions come down to a failed capacitor or fan motor, which we stock on our service trucks for same‑day fixes.

5) Thermostat or control issues

Sometimes the AC is fine, but the brain is confused. Incorrect settings, sensor placement, low batteries, or zoning faults can make the system run without delivering the temperature you expect.

Quick homeowner checks:

1. Set the thermostat to Cool, Fan Auto, and a setpoint at least 5 degrees below room temp.
2. Replace batteries and verify the display is not in a schedule hold.
3. If you have multiple zones, make sure the correct zone is calling and dampers are not stuck.

What our techs verify:

1. Thermostat calibration and placement away from heat sources and sunlight.
2. Low‑voltage control wiring integrity and fuses.
3. Proper staging for two‑stage or variable‑speed systems so you get full capacity on hot afternoons.

In homes around the Perimeter where additions created mixed duct runs, we often find a zoning damper or control board issue behind uneven cooling.

6) Duct leaks, crushed flex, or closed registers

Conditioned air lost to the attic or crawlspace never cools your rooms. Leaky ducts, disconnected boots, crushed flex runs, or decorative grills that are partially blocked can make the AC run non‑stop while comfort lags.

How to spot duct problems:

1. Rooms far from the air handler feel warm while nearby rooms are fine.
2. Dusty or musty odors when the fan runs.
3. Vents with low flow even at full fan speed.

Our solution path:

1. Measure static pressure, then inspect for kinks, crushed flex, or loose connections at plenums and boots.
2. Seal accessible joints, correct sagging flex, and balance airflow to each room.
3. Recommend right‑sized returns or additional returns when the system is starved.

This is one reason our Total Comfort Service Plan emphasizes semi‑annual maintenance. Small duct issues caught in spring prevent comfort complaints during July heat waves.

7) A dirty outdoor condenser or blocked airflow

Your outdoor unit must pull large volumes of air through the coil to dump indoor heat. Cottonwood, pine straw, grass clippings, or pressure‑washer damage can cripple heat rejection and leave you with warm supply air.

Homeowner checklist:

1. Maintain at least 18 inches of clearance around the condenser.
2. Gently rinse the coil from inside out using low pressure. Do not bend fins.
3. Keep pets from urinating on the unit, which corrodes fins and base pans.

What we do on a service call:

1. Clean the condenser cabinet and straighten fins for proper airflow.
2. Verify temperature split across the condenser coil.
3. Confirm the fan blade pitch and motor are within spec and the contactor is clean.

If your system is over 12 to 15 years old and limping along in extreme heat, we also discuss replacement options. As a Trane Authorized Dealer, we provide new system proposals with available financing and help you navigate manufacturer discounts and rebates when applicable.

How Moncrief diagnoses and fixes “running but not cooling” problems

We start with on‑site diagnostics. That includes electrical checks, refrigerant measurements, blower and condenser testing, thermostat validation, and a written, upfront assessment at your consultation. You get repair options, transparent pricing, and guidance on repair versus replacement based on age, parts availability, and maintenance history.

Two hard facts you can count on:

1. Moncrief is Atlanta’s oldest HVAC company, serving local homes since 1898.
2. Our technicians are licensed, insured, professionally trained, background checked, and drug tested. You get a trusted pro at your door, not a guess.

Want to skip future surprises? Our plan members receive twice‑yearly tune‑ups and guaranteed same‑day service, with parts and labor included on covered repairs. That is real protection when the heat index tops 100 on an August afternoon.

Special Offers for Atlanta Homeowners

• $50 off any emergency HVAC or plumbing repair over $250. Call 770-341-2178 and mention the emergency repair offer.
• We will credit your recent HVAC repair toward a new system, up to $1,000 with proof of repair in the last 12 months.
• Save $50 on our Total Comfort Service Plan. Members receive twice‑yearly tune‑ups and included parts and labor on covered repairs, plus guaranteed same‑day service.

Ready to save? Schedule at https://moncriefair.com/ or call 770-341-2178 today.

What Homeowners Are Saying

"My AC went out the middle of July. They came out on the same day and were able to diagnose my problem and schedule the repair ASAP. The technician was professional, knowledgeable and friendly... This was the most efficient repair experience I've had in a very long time." –Atlanta Homeowner

"Very grateful for same day service on this very hot day in Atlanta, friendly service and fixed our AC within an hour!! Thank you Moncrief!!!" –Atlanta Homeowner

"He discovered the problem with my air conditioner right away and immediately rectified it. It was altogether an outstanding experience. I highly recommend Moncrief Heating and Air!" –Atlanta Homeowner

"Our roof-mounted AC went out on a Tuesday... They had a tech out on a Sunday, within 3-4 hours, with a ladder, who was able to fix the issue on-site no problem. A lifesaver!" –Metro Atlanta Homeowner

Frequently Asked Questions

Why is my AC running but not blowing cold air?

A dirty filter, low refrigerant, a frozen coil, or an outdoor fan problem can stop heat transfer. Start with a fresh filter and clear vents. If air is still warm, call for diagnostics so we can check refrigerant charge, coils, capacitors, and controls.

Can I keep running the AC if the lines are iced?

No. Turn cooling off and set the fan to On to thaw the coil. Running while frozen can damage the compressor. Once thawed, we can find the root cause such as low airflow, low refrigerant, or a stuck expansion device.

How often should I change my AC filter in Atlanta?

In summer, replace 1‑inch filters every 30 to 60 days. Homes with pets, renovations, or heavy pollen may need monthly changes. Media filters last longer but still need checks each season.

When is repair better than replacement?

If the system is under 10 years old, parts are available, and the coil or compressor is healthy, repair is often best. We recommend replacement when efficiency, reliability, or major components make repair uneconomical.

Do you offer same‑day service and financing?

Yes. We provide same‑day and emergency availability. For replacements, we help with financing options subject to credit approval and guide you through available manufacturer discounts or rebates.

In Summary

When your AC is running but not cooling, the fix usually starts with airflow, refrigerant, or controls. Our Atlanta team brings 125+ years of local know‑how, same‑day AC repair, and clear, upfront solutions. Need fast help with AC running but not cooling in Atlanta or nearby? Call 770-341-2178, schedule at https://moncriefair.com/, or mention our $50 emergency repair discount to save today.

Get Fast, Expert AC Repair Today

• Call now: 770-341-2178
• Schedule online: https://moncriefair.com/
• Current savings: $50 off emergency repairs over $250, plus up to $1,000 credit toward a new system with qualifying recent repair.

We will diagnose the problem on‑site, explain your options upfront, and restore cool comfort fast. Same‑day and emergency service available across Atlanta, Sandy Springs, Roswell, Alpharetta, Marietta, and more.

Moncrief Heating & Air Conditioning has served Atlanta since 1898. Our licensed, insured, and background‑checked technicians deliver same‑day service, clear pricing, and meticulous workmanship. We are a Trane Authorized Dealer and now part of the Ace Hardware family. Ask about our Total Comfort Service Plan with twice‑yearly tune‑ups and included parts and labor on covered repairs. From Buckhead to Alpharetta, we bring local expertise, rigorous training, and a satisfaction‑first culture to every visit.