7 Signs Your AC Needs Repair (And What They Mean)
Not sure if that noise or warm air is serious? Here's how to identify common AC problems before they become emergencies—and understand what each symptom actually indicates.
Your AC doesn't fail without warning. It usually gives you signs first—sounds, smells, performance changes. The question is whether you recognize them and act before a small problem becomes an expensive emergency.
Here are seven common warning signs, what they typically mean, and how urgently you should address them.
1. Warm Air Coming From Vents
What you notice: The system is running, but the air from your vents isn't cold—or barely cool.
What it usually means:
- Thermostat issue: Check that it's set to "Cool" and the temperature is set below room temperature
- Dirty air filter: Severely restricted airflow can cause the coil to freeze and reduce cooling
- Low refrigerant: If there's a leak, the system can't absorb enough heat to cool effectively
- Compressor problems: If the compressor isn't running or is failing, no cooling happens
What to do: Check your thermostat and filter first. If both are fine and the problem persists, schedule a diagnostic—the system is working hard without producing results, which can cause further damage.
2. Ice on Refrigerant Lines or Indoor Coil
What you notice: Frost or ice buildup on the copper lines coming from your indoor unit, or visible ice on the evaporator coil.
What it usually means:
- Airflow restriction: A clogged filter, blocked return, or failing blower prevents warm air from passing over the coil
- Low refrigerant: The coil gets too cold because there isn't enough refrigerant to absorb heat properly
- Dirty evaporator coil: Insulates the coil and prevents proper heat transfer
What to do: Turn off the AC immediately and let the ice melt (this can take several hours). Check your filter. If the filter is clean, you need a professional to diagnose whether it's a refrigerant leak or another issue. Running an iced system causes compressor damage.
3. Water Leaking Around Indoor Unit
What you notice: Water pooling around your air handler, dripping from the ceiling (if unit is in attic), or water stains.
What it usually means:
- Clogged condensate drain: The drain line that removes moisture is blocked with algae or debris
- Drain pan issues: The pan is cracked, rusted, or overflowing
- Frozen coil thawing: If the coil froze and is now melting, it can overwhelm the drain system
What to do: Address this promptly—water damage to ceilings, walls, and flooring can be expensive. Turn off the system to stop condensation production. A technician can clear the drain and check for underlying issues.
4. Strange Noises When Running
What you notice: New sounds like grinding, squealing, banging, or rattling that weren't there before.
What it usually means:
- Grinding: Often motor bearings failing—needs attention before complete failure
- Squealing: Belt problems (older systems) or motor issues
- Banging/clanking: Loose or broken component inside the unit, possibly a blower wheel
- Rattling: Could be debris, loose panels, or failing components
- Clicking: Normal at startup/shutdown, but persistent clicking suggests a relay or control problem
What to do: Turn off the system if the noise is severe (grinding, banging). Running it could cause additional damage. Schedule a diagnostic before the component fails completely.
5. System Frequently Turns On and Off (Short Cycling)
What you notice: The AC turns on, runs for just a few minutes, shuts off, then starts again—repeating this cycle frequently.
What it usually means:
- Oversized system: Cools too quickly, shuts off before removing humidity, then cycles again
- Thermostat issues: Faulty thermostat or one in a bad location (near a vent or sunny window)
- Refrigerant problems: Low charge can cause pressure-related shutoffs
- Electrical issues: Failing capacitor or contactor
- Dirty filter: Overheating can trigger safety shutoffs
What to do: Check your filter first. Short cycling is hard on the compressor (the most expensive component) and needs to be diagnosed. It also fails to control humidity properly.
6. Weak Airflow From Vents
What you notice: Air coming from vents feels weaker than normal, even though the system is running.
What it usually means:
- Clogged filter: The most common cause—check this first
- Blower problems: Motor running slow, failing capacitor, or dirty blower wheel
- Ductwork issues: Disconnected ducts, major leaks, or collapsed flex duct
- Blocked vents: Closed or obstructed supply or return vents
What to do: Replace your filter if it's dirty. If airflow is weak from all vents, it's likely a blower or central duct issue. If only one or two vents are affected, the problem is probably in the branch ductwork to those areas.
7. Unusual Smells When AC Runs
What you notice: Strange odors coming from vents when the system runs—musty, burning, or chemical smells.
What it usually means:
- Musty/moldy smell: Moisture problem—mold in ductwork, on coils, or in drain pan
- Burning smell: Electrical issue, overheating motor, or dust burning off (normal briefly at first use of season)
- Rotten egg smell: Could indicate a dead animal in ductwork or a natural gas leak (leave immediately if you suspect gas)
- Chemical smell: Possible refrigerant leak
What to do: A brief burning smell at seasonal startup is usually just dust burning off. Persistent burning, chemical, or gas smells warrant turning off the system and calling for service. Musty smells indicate mold that should be addressed for air quality.
When to Call Immediately vs. Schedule Soon
Call immediately if:
- You smell gas or suspect a gas leak
- You see sparks or smoke
- There's significant water damage happening
- Carbon monoxide detector is alerting (leave the house first)
Schedule soon (within a few days) if:
- Ice is forming on the system
- Strange noises have started
- System is short cycling
- Water is leaking (if not causing immediate damage)
Can wait for convenient scheduling if:
- Airflow seems slightly reduced (after checking the filter)
- System is running but not as efficiently as before
- Minor increase in humidity levels
The difference between a $200 repair and a $2,000 repair is often just time. Catching problems early—before they cascade into bigger failures—saves money and prevents uncomfortable emergency situations.
What Happens When You Ignore the Signs
We see it often: homeowners ignore a small noise or slightly warm air, hoping it will go away. Here's what typically happens:
- A failing capacitor becomes a burned-out motor
- A small refrigerant leak becomes compressor damage
- A clogged drain becomes ceiling damage and mold
- A dirty coil becomes a frozen, damaged system
The original problem would have been fixable. The cascading damage often isn't—or costs significantly more to address.
Our Approach to Diagnosis
When you call us with any of these symptoms, we don't guess. We systematically test to find the actual cause, document what we find with photos, and explain your options before recommending any repair.
Our diagnostic fee is $129, which is applied toward the repair if you proceed. You'll see exactly what we see—no mystery, no pressure.
Crazy Comfort Team
With nearly 30 years of combined experience diagnosing and repairing HVAC systems in Texas, we've seen every symptom and understand what they actually mean.