Repair help
13 Common AC Problems and How to Fix Them
AAZparts Team
Updated on July 31, 2025
8 min read
If your air conditioner isn’t working properly, whether it’s blowing warm air, making strange noises or giving off a bad smell, you’re in the right place. This guide will walk you through what might be causing the ac problem and show you how to check and fix it in simple steps. From weak airflow to unusual noises, early action can save you time and money. Explore expert tips and get your AC back in top state at AZParts.
1. AC Not Turning On
One of the most frustrating AC problems is when the unit doesn’t turn on at all. This could be due to a tripped circuit breaker, a blown fuse, or a faulty thermostat.
Start by checking your power source and resetting your breaker. If the issue persists, inspect the contactor or AC capacitor. These components are easy to replace with basic tools available at AZParts, where you can find high-quality replacement parts for your AC system.
2. AC Not Blowing Cold Air
When your AC runs but doesn’t cool, the cause may be a dirty air filter, low refrigerant levels, or a clogged condenser coil. These AC problems reduce system efficiency and airflow.
First, try replacing the air filter. If that doesn't help, clean the coils and check the refrigerant line for visible damage. AZParts offers essential cleaning air conditioner parts to help you troubleshoot and restore cooling performance on your own.
The air conditioner is running, but it is not blowing cold air as expected (Source: AZParts)
3. AC Freezing Up (Indoor or Outdoor Unit)
Frozen air conditioners are among the most common AC problems, often caused by restricted airflow or low refrigerant.
Indoor Unit Freezing
- Dirty Air Filter: A clogged filter restricts airflow, causing the evaporator coil to freeze. Replace the filter regularly.
- Blocked Vents or Ducts: Ensure vents are open and unblocked to maintain circulation.
- Frozen Evaporator Coil: Turn off the system and let it thaw before checking for dirt or debris on the coil.
Outdoor Unit Freezing
- Low Refrigerant: A refrigerant leak can lead to ice buildup on the coil. Look for visible frost on the refrigerant line.
- Dirty Condenser Coils: Debris can block heat exchange. Clean the coils carefully to restore proper function.
- Faulty Thermostat: If the system doesn't cycle off correctly, it may overcool and freeze. Calibration or replacement might be needed.
4. AC Leaking Water (Inside or Outside)
Water leaks are another frequent AC problem, often signaling a drainage or moisture issue. It's important to determine whether the leak is happening inside or outside your home.
Leaking Water Inside
- Clogged Drain Line: Dirt, mold, or algae can block the condensate line, causing overflow. Cleaning the line usually resolves the issue.
- Cracked or Rusted Drain Pan: A damaged pan beneath the evaporator coil may cause dripping. Replacement is a straightforward solution.
- Unit Not Level: If the indoor unit isn't properly sloped, water may not drain correctly.
Leaking Water Outside
- Excessive Water After Freezing: When a frozen coil melts, the resulting water may pool temporarily.
- Cracked Exterior Drain Pipe: Damage from heat or aging can lead to leaks near the outdoor unit. Replacing the pipe solves the problem.
- Blocked Drain Outlet: Leaves or dirt may obstruct the drain's exit point. Clear it to ensure proper water flow.
AC is leaking water (Source: AZParts)
5. AC Running Constantly
If your air conditioner never seems to shut off, it may be due to incorrect thermostat settings, dirty coils, or a malfunctioning relay switch. These AC problems can lead to higher energy bills and increased wear.
Inspect your thermostat and system settings first, then clean both indoor and outdoor coils.If needed, you can still maintain better control over your system by checking thermostat settings regularly and scheduling routine maintenance to avoid overuse.
The AC unit continues to operate constantly without cycling off (Source: AZParts)
6. Hot Air Blowing from AC
When your AC starts blowing hot air instead of cold, it's a sign of low refrigerant, a faulty compressor, or a dirty condenser. These AC problems are fixable with the right tools and parts. Begin by cleaning your outdoor unit and checking for refrigerant leaks.
For more advanced repairs, it's best to have your unit checked by a technician, especially if cleaning and basic checks don’t solve the issue. You can still explore AZParts for helpful tips and guidance on how to troubleshoot common AC problems at home.
7. AC Turning On and Off Frequently (Short Cycling)
Short cycling is when your AC unit turns on and off repeatedly without completing a full cooling cycle. This is not just inefficient, it's also one of the most damaging AC problems over time, putting stress on your compressor and driving up energy bills. Causes can range from dirty air filters and frozen coils to a thermostat that's installed too close to a vent or heat source.
Sometimes, short cycling may result from an oversized AC unit that cools too fast and shuts off prematurely. Homeowners can often resolve the issue by replacing air filters, ensuring vents are unobstructed, or repositioning the thermostat. However, if the problem persists, it may be time for a deeper inspection.
The air conditioner keeps turning on and off repeatedly in short intervals (Source: AZParts)
8. AC Tripping Circuit Breaker Repeatedly
If your air conditioner is constantly tripping the circuit breaker, that’s a clear sign of electrical overload and one of the more serious AC problems. This could be due to a dirty filter making the system overwork, or more critically, a failing compressor drawing too much current.
You should clean or replace the air filter, then inspect the outdoor unit for dirt buildup. If the breaker still trips, stop using the unit and have a technician check the capacitor or compressor.
9. Weird Noises from the AC Unit
Strange sounds from your AC unit are often early warning signs of mechanical or electrical trouble. Buzzing could indicate loose parts or debris in the outdoor unit. A grinding noise typically points to worn motor bearings, while clicking noises can suggest a failing thermostat or electrical relay. A hissing sound might even indicate a refrigerant leak. Addressing these sounds promptly can prevent further damage.
To fix this, turn off the unit and check for loose parts or debris. If the noise persists or sounds mechanical, avoid further use and contact a technician to prevent damage.
Weird noise coming from AC is very irritating (Source: AZParts)
10. Strange Smells from the System
Unpleasant odors coming from your AC system are often more than just a nuisance, they usually point to deeper AC problems.
- A musty smell often means mold or mildew has formed on the coils or inside the ductwork.
- A burning smell may indicate overheating wires or motor components, which should be inspected immediately.
- A lingering cigarette smell, especially in homes where smoking once occurred, is another common complaint.
Smoke particles can become embedded in the filter or interior plastic parts, recirculating every time the unit runs. In such cases, the most effective fix is to replace smoke-saturated filters and covers to help your AC breathe clean again.
11. Electric Control Failure
Electric control failure is a common issue in aging air conditioning units, particularly those that cycle on and off frequently. Over time, components like contactors, relays, and capacitors degrade, leading to erratic cooling, startup issues, or even complete system failure. One of the most frequent causes is a faulty capacitor, which plays a key role in helping the compressor and fan motors function properly.
If your system hums but fails to start, or shuts off prematurely, a failing capacitor could be the reason. For those comfortable with electrical repairs, replacing this part can restore proper function, and quality AC capacitors compatible with most systems are readily available from AZParts.
Worn-out or damaged electrical controls can prevent the fan or compressor from working (Source: AZParts)
12. Sensor Problems
Your air conditioner relies on a thermostat sensor to monitor room temperature and regulate cooling cycles. If the sensor becomes dislodged or misaligned, especially near the evaporator coil, it can cause irregular cooling behavior. You might notice the AC turning on and off at strange times, or failing to maintain a stable room temperature.
In most cases, the fix is simple, gently reposition the sensor so it’s close to the coil without touching it. If it’s damaged or unresponsive, replacing the sensor is a straightforward task for most DIYers.
13. Refrigerant Leak on Air Conditioner
Among all AC problems, refrigerant leaks are especially critical, as they directly affect cooling performance and can damage the compressor if left unresolved. Symptoms of a leak include reduced airflow, ice formation on the evaporator coil, or a hissing noise near the refrigerant lines. While professional servicing is recommended for major leaks, DIYers may address minor issues using sealants or by topping up refrigerant carefully.
In such cases, a piercing valve is essential; it allows access to sealed systems for recharging or pressure checks. AZParts offers reliable, easy-to-install AC piercing valves that are ideal for temporary service connections, making them a practical tool for at-home AC maintenance.
Coolant is leaking, so the AC can’t cool properly and may overwork (Source: AZParts)
Common AC problems like poor cooling, frequent cycling, or strange noises are often caused by worn-out parts such as fan motors, AC capacitors, control boards, piercing valves, AC port adapters, or even AC protective covers. If you're looking for reliable, high-quality AC parts to fix the issue, come to AZParts. We offer a wide range of trusted components to keep your cooling system running smoothly.
Explore more about other air conditioner's issues:
Contact Info
Address: 8 The Green, Ste A, Dover, Delaware 19901-3618, United States
Email: support@azparts.com
Air conditioner
- 1. AC Not Turning On
- 2. AC Not Blowing Cold Air
- 3. AC Freezing Up (Indoor or Outdoor Unit)
- 4. AC Leaking Water (Inside or Outside)
- 5. AC Running Constantly
- 6. Hot Air Blowing from AC
- 7. AC Turning On and Off Frequently (Short Cycling)
- 8. AC Tripping Circuit Breaker Repeatedly
- 9. Weird Noises from the AC Unit
- 10. Strange Smells from the System
- 11. Electric Control Failure
- 12. Sensor Problems
- 13. Refrigerant Leak on Air Conditioner
Further Reading
Further Reading
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