Carrollton HVAC Repair: AC Running but Not Cooling

Estimated Read Time: 10 minutes

If your air conditioner is running but not cooling, you’re not alone. North Texas heat pushes systems hard, and a small issue can leave your home warm and humid. This guide covers the seven most common causes, quick checks you can try, and when to call a pro for safe, lasting repairs. Prefer to skip the guesswork? Southern Comfort Mechanical offers 24/7 service and same‑day or next‑day appointments across DFW.

1) Dirty or Clogged Air Filter

A dirty return filter is the simplest reason an AC runs without delivering cool air. Reduced airflow starves the evaporator coil of warm air. The coil can get too cold and ice over, which blocks airflow even more and warms the home.

Try this:

Check your return filter size and condition. If it looks gray, dusty, or bowed, replace it.
Make sure no furniture or rugs block return vents.
Set your thermostat to “On” for 20–30 minutes after replacing an extremely dirty filter to help thaw a lightly frosted coil.

Signs you need a pro:

Persistent ice, even with a clean filter.
Burning smells, tripped breakers, or short cycling.

Pro tip: In DFW, cottonwood and construction dust peak in spring. Many homes need filter changes every 30–60 days in May through August.

"Prompt, knowledgeable and thorough... identified a pinched air duct... everything has been ok since then."

2) Frozen Evaporator Coil

If air from the vents feels weak or warm and you see frost on the indoor coil or refrigerant lines, the system may be frozen. Causes include low airflow from a clogged filter, a failing blower motor, or incorrect refrigerant levels.

What you can do:

Turn the system off at the thermostat and set the fan to “On” to thaw the coil.
Replace the filter if dirty and clear supply and return vents.
After thawing, restart cooling and monitor temperatures at a couple of supply vents.

When to call us:

Ice returns within hours.
You hear the blower starting and stopping or humming without moving air.
You see standing water near the air handler after thawing.

Why it matters: A frozen coil can bend fins, flood the drain pan, and cause water damage. Quick diagnosis saves the coil and prevents ceiling leaks.

"Cody was excellent with the service call and fixed our problem right away."

3) Low Refrigerant or a Refrigerant Leak

Refrigerant absorbs heat indoors and releases it outside. If levels are low due to a leak, the coil can’t absorb heat, so the system runs and runs but supply air stays warm. Adding refrigerant without fixing the leak is a short‑term patch and can damage the compressor.

Your safe checks:

Look for frost on the larger insulated copper line.
Listen for hissing at line sets or the indoor coil area.
Note longer run times and rising utility bills.

What a technician does:

Perform electronic leak detection or nitrogen pressure testing.
Repair or replace leaking components.
Weigh in the factory‑specified refrigerant charge and verify performance.

DFW insight: Attic systems in older Denton County homes often have line sets that pass through tight chases. Vibration wear and insulation gaps increase leak risks.

"Sameday service. Josh quickly diagnosed problem and had repair parts with him... promptly up and running again."

4) Blocked or Dirty Outdoor Condenser Coil

Your outdoor unit must dump indoor heat into the outside air. If the condenser coil is matted with lint, grass clippings, or cottonwood, heat stays trapped. The AC runs but can’t cool effectively, especially during late‑afternoon heat.

DIY steps:

Turn off power at the disconnect before touching the unit.
Gently rinse the outside coil fins from top to bottom. Do not use high pressure.
Keep shrubs at least two feet away from all sides of the unit.

Call a pro if:

You hear rattling or grinding from the condenser fan.
Circuit breakers trip during peak heat.
Coil fins are bent or collapsed.

Why it matters: A dirty coil can raise head pressure and overheat the compressor. Professional cleaning and amp‑draw checks restore capacity and protect your system.

"Southern Comfort Mechanical did an amazing job... Cleaned, put back together, running, the house is cool and AC is running."

5) Fan Problems: Blower or Condenser Fan Issues

Airflow is the engine of cooling. If the indoor blower or outdoor condenser fan fails, you lose heat transfer. You might feel warm air at vents, hear the outdoor compressor humming, or notice the outdoor fan not spinning.

What you can observe safely:

Check whether the outdoor fan spins when the system is cooling.
Feel for air strength at several supply vents.
Listen for squeals or scraping that point to motor or bearing problems.

Common fixes by a technician:

Replace worn capacitors or fan motors.
Correct blower speeds to match duct design and tonnage.
Balance and clean blower wheels for better airflow and efficiency.

Good to know: Undersized return air or a dirty blower wheel can mimic motor failure. A full static pressure test identifies the real bottleneck.

"Ivan... Professional and detail oriented. Did a great job and fixed all my problems."

6) Thermostat or Control Issues

Sometimes the problem is your controls, not the equipment. Incorrect thermostat settings, failed sensors, or a miswired smart thermostat can stop cooling.

Quick checks:

Confirm the thermostat is set to Cool and the fan is set to Auto.
Replace thermostat batteries if applicable.
If you recently installed a smart thermostat, verify that the common wire is connected and the equipment type is programmed correctly.

When to involve a pro:

The system clicks but does not start.
Cooling starts, then stops within a minute.
Heat turns on when you call for cooling.

What we do:

Test low‑voltage circuits and safety controls.
Update programming for heat pump, dual‑fuel, or multi‑stage systems.
Replace faulty sensors or boards and verify safe operation.

"He explained what was happening and made sure we were ready for the season."

7) Duct Leaks, Poor Insulation, or Attic Heat Gain

In many Dallas–Fort Worth homes, the AC is fine but the conditioned air never reaches rooms. Leaky or pinched ducts, missing mastic, and uninsulated boots dump cold air into a 130‑degree attic. You pay for cooling you never feel.

What you can spot:

Rooms far from the air handler are warmer.
Dusty returns and hot second floors during the afternoon.
Kinks in flex duct or disconnected runs near the plenum.

Fixes that work:

Pressure test the duct system to locate leaks.
Seal with mastic and tape rated for HVAC, then insulate as needed.
Improve attic insulation and verify proper soffit and ridge ventilation.

Local detail: In older Carrollton and Denton homes, flex ducts were often added later to serve additions. These branches are prone to sags that restrict airflow.

"He checked the air flow and temperature at several heat registers and identified a pinched air duct. He straightened it out and everything has been ok since then."

When a Professional Repair Is the Smart Move

DIY checks are helpful, but certain conditions call for a licensed HVAC pro:

Refrigerant leaks, icing that returns, or hissing lines.
Electrical smells, repeated breaker trips, or visible arcing.
Water near the air handler, a clogged drain, or ceiling stains.
Fan motors that will not start or stop randomly.
Systems over 10 years old with rising energy bills or uneven cooling.

What to expect from Southern Comfort Mechanical:

Rapid response with 24/7 availability and honest recommendations.
NATE‑certified technicians using advanced diagnostics to find root causes.
Fully stocked trucks for same‑day fixes on common parts.
Clear pricing before work begins and follow‑up support.

Membership matters: Our Comfort Club includes bi‑annual tune‑ups, priority scheduling, and member‑only discounts that help prevent breakdowns in peak season.

Prevent It Before It Starts: DFW‑Focused Maintenance Tips

Regular maintenance keeps capacity high and bills low through summer:

Change filters every 30–60 days in peak season.
Hose off the outdoor coil each spring and keep a 2‑foot clearance.
Pour a cup of vinegar into the condensate drain line at the start of summer.
Test your thermostat and replace low batteries before the first heat wave.
Schedule spring AC and fall heat tune‑ups to catch small problems early.

What our tune‑ups include:

Full system inspection and electrical testing.
Outdoor coil rinse and inspection.
Refrigerant level verification and safety control testing.
Airflow checks and temperature splits to confirm capacity.

Fact check you can trust:

Licensed in Texas, HVAC license TACLA104577C.
NATE‑certified technicians with ongoing training.
Multi‑year Best of Denton County recognition and active in local chambers.

Ready to feel real cold air again? We service all brands across Dallas, Fort Worth, Denton, Plano, Irving, Garland, Frisco, Grand Prairie, and Carrollton.

Frequently Asked Questions

Why is my AC running but blowing warm air?

Common causes include a dirty filter, frozen coil, low refrigerant, a blocked outdoor coil, or fan problems. Start with a fresh filter and clear debris outside. If air is still warm, schedule professional diagnostics.

Can low refrigerant damage my AC?

Yes. Low refrigerant causes the evaporator coil to ice and the compressor to overheat. Running in this condition can shorten compressor life. A licensed tech must find and fix the leak, then weigh in the correct charge.

How long should an AC run before I feel cooler air?

Most systems should deliver cooler air within minutes and start lowering room temperature within 15–20 minutes. If not, check the filter and outdoor unit. Persistent issues deserve a professional check.

Should I turn off my AC if I see ice?

Yes. Turn cooling off and set the fan to On to thaw the coil. Replace a dirty filter. If ice returns after thawing, call for service to prevent water damage and further icing.

How often should I change my filter in DFW?

Every 30–60 days in peak summer, more often if you have pets or construction nearby. Cottonwood and dust increase clogging in late spring across North Texas.

In Summary

When your air conditioner is running but not cooling, the fix could be as simple as a filter or as serious as a refrigerant leak. Use the steps above for quick checks, then lean on a licensed, NATE‑certified team for safe repairs and lasting comfort.

Ready for Fast, Local Help?

Southern Comfort Mechanical is standing by 24/7 across Dallas–Fort Worth. Call (469) 515-7987 or schedule at https://scmdfwair.com/ for same‑day or next‑day service. Ask about our Comfort Club tune‑ups for season‑long reliability.

Call now: (469) 515-7987 • Book online: https://scmdfwair.com/ • 24/7 emergency service available across DFW. Ask about Comfort Club for priority service and savings.

About Southern Comfort Mechanical

Southern Comfort Mechanical serves Dallas–Fort Worth with people‑first HVAC service, 24/7 emergency response, and straightforward pricing. Our technicians are NATE‑certified and continuously trained, and we service all brands. We are a multi‑year Best of Denton County winner and stand behind our work with a 100% satisfaction commitment. Licensed and insured: HVAC TACLA104577C. We offer financing options for replacements and a Comfort Club with bi‑annual tune‑ups. Local insight, fast diagnostics, and quality workmanship are our daily standards.