Is Your AC Acting Up Again? Here’s How to Solve the Most Common Air Conditioner Problems

It’s one of the worst feelings—walking into your home on a sweltering summer day only to find your AC not cooling like it should. Maybe it’s blowing warm air, cycling nonstop, or just won’t turn on at all. Sound familiar?

You’re not the only one dealing with it.

Across the U.S., thousands of homeowners run into common air conditioner problems every summer—and most of them don’t know what’s really going wrong, or how serious it might be.

Understanding the early signs of trouble can save you time, money, and a whole lot of stress.

Read on to understand the most common AC problems, so that you know when it’s time to call in a professional before small problems with the air conditioner turn into expensive repairs.

1. Dirty Air Filter: The #1 Cause of Cooling Issues

Let’s start with the simplest fix.

If your AC isn’t cooling like it used to—or it’s constantly running—a dirty or clogged air filter is often the culprit.

What’s Happening?

Your air filter traps dust, dirt, and allergens from circulating in your home. But when it gets too full, it blocks airflow. That makes your system work harder, which reduces efficiency and may even cause the evaporator coil to freeze.

What You Can Do?

• Check your air filter monthly
• Replace it every 1-3 months (or more often if you have pets or allergies)
• Make this part of your routine maintenance—it’s quick, cheap, and effective

Pro tip: Set a reminder on your phone so you don’t forget.

2. Thermostat Trouble: Not Always the AC’s Fault

Think your AC isn’t working? Double-check your thermostat settings first.

What’s Happening?

The thermostat tells your system when to turn on and off. If it’s miscalibrated, has low batteries, or is located in a poor spot (like next to a sunny window), it may not be reading your home’s actual temperature.

What You Can Do?

• Make sure it’s set to “cool” (it happens more often than you’d think!)
• Set the temp at least 5°F lower than the current room temp
• If it’s battery-powered, swap in fresh batteries
• Consider upgrading to a smart thermostat for better control

3. Refrigerant Leaks: A Silent AC Killer

Refrigerant is the lifeblood of your AC. Without it, your system can’t cool your home. But refrigerant leaks are hard to detect and can cause long-term damage.

What’s Happening?

Low refrigerant = reduced cooling. It could also cause:

• Hissing or bubbling sounds
• Ice on refrigerant lines
• A sudden spike in your energy bill

Why You Shouldn’t DIY

Refrigerant is a hazardous chemical and should only be handled by licensed HVAC professionals.

If you see these signs, shut off the AC and call a technician immediately.

4. Frozen Evaporator Coils: Cold Isn’t Always Good

If your AC isn’t pushing out air at all—or if the air is warm—frozen evaporator coils might be the issue. This is one of the most common and costly problems people overlook.

What’s Happening?

The evaporator coil inside your indoor unit is responsible for absorbing heat from your home. But when something disrupts the process—like restricted airflow, low refrigerant levels, or dirty coils—the coil gets too cold and freezes over.

That ice blocks airflow even more, causing a chain reaction that can:

• Reduce cooling efficiency
• Create uneven temperatures around the house
• Increase energy usage
• Strain or damage the compressor

You might notice ice on the copper lineset, water dripping from the unit, or your AC running but not cooling properly.

What You Can Do

• Turn off your AC and let the coil fully thaw (this may take several hours)
• Replace your dirty air filter to restore airflow
• Ensure all vents are open and unobstructed
• Don’t block the air return with furniture or curtains
• If freezing happens again, schedule a professional inspection. You could be dealing with low refrigerant or a damaged compressor.

Pro Tip: A frozen coil isn’t just a cooling issue—it’s a sign that your system’s heat absorption process (latent heat) is breaking down. Catching it early can prevent major repairs.

5. AC Stopped Working Suddenly? Check the Circuit Breaker

Your AC unit pulls a lot of power. A sudden shutdown might not mean your system’s broken—it could just be a tripped breaker.

What’s Happening?

Too many appliances running at once? Storm? Power surge? Any of these can trip the circuit which makes AC stop working suddenly.

What You Can Do?

• Go to your home’s electrical panel
• Find the breaker labeled “AC” or “HVAC”
• If it’s flipped, reset it once

If the breaker keeps tripping repeatedly, call an electrician or HVAC tech. This could indicate a deeper electrical and air conditioner issue or short.

6. Outdoor Unit Not Running? Check the Condenser Coils

Even if your indoor fan is blowing, your outdoor condenser unit might not be doing its job.

What’s Happening?

The outdoor unit releases the heat removed from your home. If the condenser coils are dirty or blocked by leaves and debris, heat can’t escape.

What You Can Do?

• Turn off power to the unit
• Gently rinse the coils with a hose (don’t pressure wash)
• Clear away plants or grass within 2 feet of the unit

Regular cleaning helps your system breathe and cool better.

7. AC Blowing Warm Air? It Might Be a Sensor Problem

Your system has a temperature sensor near the evaporator coil. If it shifts out of place, it throws off the cooling cycle.

What’s Happening?

The sensor reads the wrong temp, causing short cycling or warm air.

What You Can Do?

• Turn off the power
• Gently bend the sensor back into place (should be near but not touching the coil)

If unsure, call an HVAC tech. It’s a small fix—but one that needs care.

8. Water Leaking Around AC Unit? Drainage Could Be Blocked

AC units pull moisture from the air. That moisture drains through a pipe. When the line is clogged, water can back up and cause leaks or even damage your ceiling or walls.

What’s Happening?

• Algae, mold, or debris blocking the drain line
• Improper installation or leveling

What You Can Do?

• Locate the drain line (usually a white PVC pipe near your indoor unit)
• Use a wet/dry vacuum to suction out blockages
• Flush the line with a mix of vinegar and warm water every few months

9. Weak Airflow in Some Rooms? Leaky Ducts Could Be to Blame

If one room is warmer or stuffier than others, it’s not just your imagination.

What’s Happening?

Leaky ducts waste cooled air, making your AC work harder to maintain the temperature.

What You Can Do?

• Inspect exposed ductwork in attics or basements
• Seal small leaks with aluminum tape (never standard duct tape!)
• Consider a professional duct sealing service for better long-term results

10. AC Keeps Turning On and Off? Check the Capacitor or Compressor

Short cycling drains energy and wears out your system. Often, it’s a failing capacitor or compressor—two key electrical components.

What You Need to Know:

If your AC short cycles (starts and stops frequently), call a professional. Capacitor or compressor repairs require specialized tools and training.

11. Capacitor or Fan Failure

The capacitor is what gives your AC motor the “kickstart.” If your system won’t start, clicks, or starts slowly, it could be failing. A broken fan motor means your system can’t release heat — which overheats and eventually kills the compressor.

What to do?

Leave these to the pros. High-voltage components can shock or injure you.

12. Damaged Compressor: The Costliest AC Problem

The compressor is the heart of your AC. It pumps refrigerant through the system. If it’s damaged, your AC can’t cool—period.

Signs of a Bad Compressor:

• AC won’t turn on or makes loud noises
• Tripped circuit breaker
• Warm air blowing despite thermostat settings
• High energy bills

Why It Happens:

• Electrical issues
• Refrigerant problems
• Dirty coils or blocked airflow

Call a pro. Compressor issues are complex and expensive—usually not worth a DIY attempt.

13. Capacitor Failure: No Power, No Cooling

Capacitor stores and delivers the energy your AC needs to start the compressor and fan motors.

Symptoms:

• Clicking noise when starting
• AC won’t turn on
• Humming but no cooling
• Starts then shuts off

Why It Happens:

• Heat damage
• Wear over time
• Power surges

14. Outdoor Fan Failure: When the Unit Can’t Breathe

The outdoor fan helps release heat outside your home. If it fails, the system overheats and shuts down.

Signs of Trouble:

• AC shuts down randomly
• Outdoor fan not spinning
• Strange grinding or squealing sounds

What You Can Do:

• Check for visible debris or obstructions
• Listen for noise from the outdoor unit

15. Strange Smells: Don’t Ignore the Odor

DIY or Call a Pro?

• Musty = DIY clean
• Burning or gas = Professional, immediately

Pro Tip: Any burning, rotten, or chemical smell is a red flag. Don’t wait—shut off your system and call a professional.

16. Thermostat Miscalibration: It’s Not Just the Settings

A miscalibrated thermostat sends incorrect signals—causing overcooling, undercooling, or constant cycling.

What You Can Do:

• Ensure it’s not exposed to sunlight or near heat-producing devices
• Check if it’s level (older models need this)
• Upgrade to a smart thermostat to auto-calibrate and save money

17. Leaky Ducts: Wasting Air, Wasting Money

Up to 30% of your cooled air could be leaking through cracks or gaps in your ducts.

Signs:

• Hot/cold spots in rooms
• High energy bills
• Dust buildup near vents

What You Can Do:

• Check visible ductwork in attics/basements
• Seal small gaps with aluminum foil tape

When to DIY and When to Call a Pro

Problem	DIY?	Call a Pro?
Dirty Filter	✅	❌
Thermostat Settings	✅	❌
Circuit Breaker Reset	✅	❌
Drain Line Cleaning	✅	❌
Refrigerant Leak	❌	✅
Compressor/Capacitor	❌	✅
Fan Motor Issues	❌	✅
Electrical Burning Smell	❌	✅

Safety Note: If you’re not 100% sure what you’re doing, don’t risk it. High-voltage components, refrigerant exposure, and electrical faults can be dangerous.

Seasonal Maintenance Checklist

Stay ahead of the problems. Follow this simple quarterly schedule:

Every 1–3 Months

• Replace air filters
• Check thermostat settings
• Make sure vents are open and unblocked

Every 6 Months

• Rinse outdoor condenser coils
• Clear 2 ft. space around outdoor unit
• Flush drain line with vinegar/warm water mix

Every 12 Months

• Professional AC tune-up and inspection
• Ductwork inspection for leaks
• Thermostat calibration check

Want to do more? Join the Comfort Club for scheduled maintenance, priority service, and major discounts.

Want Lower Bills & Better Comfort?

Before you invest in a new system, try this:

• Seal ducts and insulate attic
• Use ceiling fans to circulate air
• Install blackout curtains on sunny windows
• Upgrade to a smart thermostat
• Schedule a yearly tune-up to keep your system running at peak efficiency

Want the full breakdown with expert tips? Don’t miss our essential read: 5 Ways to Save Money on Air Conditioning This Summer

Let’s Make Sure Your AC Is Running Like It Should

Still noticing common air conditioner problems? Or maybe you’re just ready to prevent future breakdowns before they start?

Whether your unit needs a quick fix, a full inspection, or you’re exploring options for a new energy-efficient model, One Hour Heating & Air Conditioning has your back.

Book an Appointment Today.

Speak with one of our certified comfort advisors—we’ll assess your system, explain your options in plain English, and help you make the smartest decision for your home and budget.

And remember, we’re always on time… or you don’t pay a dime.

This isn’t just a motto—it’s our guarantee.