AC Troubleshooting: 7 Common Problems & What to Do Before You Call

Nothing disrupts a Central Florida day faster than an air conditioner that stops working. The indoor temperature starts to climb, and so does your stress level. Before you panic and assume the worst, a little basic ac troubleshooting can often save you time, money, and worry. Many common issues have surprisingly simple solutions, but it can be hard to know where to begin or whether you’re dealing with a quick fix or a serious problem that requires an expert.

This guide was created to give you confidence. We’ll walk you through seven of the most frequent AC problems our certified technicians see, providing a simple, step-by-step process to help you safely diagnose the issue. You will learn what to check, how to handle minor fixes on your own, and gain the peace of mind that comes from knowing exactly when it’s time to call for trusted, professional service. Let’s get your home cool and comfortable again.

Start Here: 3 Simple Checks Before You Panic

When your air conditioner suddenly stops working on a hot day, it’s easy to assume a costly repair is needed. But before you pick up the phone, take a deep breath. This initial phase of ac troubleshooting is something every homeowner can do safely. These three simple checks are designed to be your first line of defense. They are quick, require no special tools, and solve a surprising number of common AC issues, potentially saving you the cost and wait of an unnecessary service call.

1. Check Your Thermostat Settings

The thermostat is the brain of your cooling system, and a simple settings error is a very common culprit. Before looking anywhere else, confirm the following:

• Is it set to ‘Cool’? It’s easy for settings to be accidentally changed. Ensure the system mode is set to “Cool” and not “Heat,” “Off,” or “Fan Only.”
• Is the temperature correct? The set temperature must be lower than the current room temperature for the AC to kick on.
• Do the batteries need replacing? If your thermostat isn’t hardwired, a dead or dying battery can prevent it from communicating with your AC unit.

2. Inspect Your Air Filter

A clogged air filter is the single most common cause of reduced cooling performance and system failure. It restricts airflow, forcing your AC to work much harder than it should. Understanding the importance of airflow is fundamental to grasping how air conditioning systems work. To check yours, locate the filter—typically in a slot on your indoor furnace or air handler, or in a large return air vent. Slide it out and hold it up to a light. If you can’t see light through it, it’s too dirty.

If your filter is visibly clogged with dust and debris, replace it with a new one of the correct size. This simple step can restore airflow and dramatically improve cooling efficiency.

3. Look at Your Circuit Breaker

Your air conditioner is a powerful appliance that draws a lot of electricity. A power surge or an overloaded circuit can cause its dedicated circuit breaker to trip as a safety precaution, cutting power to the unit. Go to your home’s main electrical panel and look for the breaker labeled for your “AC,” “Air Handler,” or “Condenser.” If a breaker is tripped, it will be in the “OFF” position or shifted to the middle. To reset it, push the switch firmly to the “OFF” position first, then flip it back to “ON.”

Important: Only attempt to reset the breaker once. If it trips again immediately, leave it off and call a trusted expert. A repeatedly tripping breaker signals a more serious electrical problem that requires professional diagnosis.

Symptom: AC Won’t Turn On At All

There’s nothing more stressful than an air conditioner that refuses to start, especially during a sweltering Florida summer. If you’ve already confirmed your thermostat has power and the circuit breaker hasn’t tripped, your ac troubleshooting journey needs to go a step deeper. While the following issues often require a professional, a quick check can give you valuable information about the problem.

Several components could be at fault, from a simple safety switch to a more complex electrical failure. Here’s what to look for before you make the call.

Check for a Clogged Condensate Drain Line

Your AC doesn’t just cool the air; it also removes humidity. This moisture is collected and funneled outside through a condensate drain line. To prevent water damage from overflows, most systems have a safety float switch that will shut down the entire unit if it detects a clog. You can usually find this PVC pipe near your indoor air handler. If you see standing water in the drain pan, a clog is the likely culprit. Keeping this line clear is a critical part of the proper air conditioner maintenance recommended by the U.S. Department of Energy to prevent unexpected shutdowns.

Examine the Outdoor Unit (Condenser)

If the indoor unit seems fine, the problem may be with the outdoor condenser. Before assuming the worst, perform a quick visual and auditory inspection. This is a vital step in any ac troubleshooting process when you suspect a power issue. Check for the following:

• The Disconnect Switch: Look for a metal box on the exterior wall near your condenser unit. Inside, there is usually a lever or breaker-style switch. Ensure it hasn’t been accidentally turned off.
• Obvious Obstructions: Heavy debris, overgrown shrubs, or yard equipment packed against the unit can sometimes interfere with its operation or safety features.
• Any Sound at All: Even if the fan isn’t spinning, you should hear a faint humming or buzzing sound when the unit is trying to start. Complete silence often points to a serious electrical issue like a failed contactor or capacitor.

If these checks don’t get your system running, it’s a clear sign of a more complex electrical or mechanical failure that requires an expert. To ensure a safe and accurate diagnosis, our experts can diagnose the issue fast.

Symptom: AC is Running, But Not Blowing Cold Air

Few things are more frustrating than hearing your air conditioner running but feeling warm air coming from the vents. This common issue indicates that while the fan is working, the cooling mechanism is not. This is a critical step in your ac troubleshooting process, separating a simple airflow problem from a more serious system failure.

Before diving into complex parts, perform one quick check: ensure your air filter is clean. A severely clogged filter can restrict airflow so much that the system can’t cool effectively. If the filter is fine, the problem likely lies with one of the core components of your AC system. These issues almost always require the expertise of a certified HVAC technician to diagnose and fix safely.

Dirty Evaporator or Condenser Coils

Your AC system has two sets of coils that work together to transfer heat out of your home. Over time, these coils can become coated in a thick layer of dust and grime. This buildup acts as an insulator, preventing the coils from absorbing and releasing heat efficiently. While you can gently rinse the outdoor condenser unit, the indoor evaporator coil is delicate and difficult to access, making it a job best left to a trusted professional.

Signs of a Refrigerant Leak

Refrigerant is the lifeblood of your air conditioner, circulating through the coils to absorb heat from inside your home and release it outside. If your system is low on refrigerant, it won’t be able to cool properly. The U.S. Department of Energy lists incorrect refrigerant charge as one of the most Common AC Problems requiring professional service. Watch for these tell-tale signs:

• A hissing or bubbling noise near the unit.
• Ice or frost forming on the copper refrigerant lines or evaporator coil.
• Air from the vents that is only slightly cool, not cold.

Because refrigerant is a hazardous substance, only a certified and licensed technician is permitted to handle it.

Potential Compressor Failure

The compressor is the heart of your AC system. It’s a powerful motor that pressurizes and pumps refrigerant through the coils to initiate the cooling cycle. If the compressor fails, the entire cooling process comes to a halt. This is one of the most significant and costly repairs an air conditioner can need, and diagnosing it correctly requires specialized tools and expertise. This is not a DIY fix and should only be handled by an experienced HVAC expert.

Symptom: Weak Airflow or Water Leaks

If you feel lukewarm air or barely any air coming from your vents, your comfort and your system’s efficiency are both at risk. Weak airflow forces your AC to run longer, driving up energy bills without cooling your home. Similarly, finding water pooled around your indoor unit is a clear signal that something is wrong. While these symptoms seem different, their causes are often linked. Your first step in any ac troubleshooting process should always be to check for a dirty air filter, as it is the most common cause of both problems.

Check All Vents and Registers

Before investigating the system itself, take a quick walk through your home. Check every supply vent to ensure it is open and unobstructed. It’s common for vents to be accidentally closed or blocked by furniture, rugs, or drapes. Blocked registers disrupt air circulation, causing uneven temperatures and putting unnecessary strain on your AC’s blower motor. Ensuring clear pathways for air is a simple fix for improving performance.

Inspect for a Frozen Evaporator Coil

Weak airflow can be caused by ice buildup on your system’s indoor evaporator coil. This layer of ice physically blocks air from passing through, drastically reducing its cooling power. The primary causes of a frozen coil are:

• A severely clogged air filter restricting airflow.
• Low refrigerant, which indicates a leak that must be fixed.

If you see ice, turn the AC’s cooling mode off immediately but leave the fan running. This will help the ice thaw safely. Important: While this thaws the coil, it does not fix the root problem. A frozen coil almost always requires a certified technician to diagnose and repair the underlying issue to prevent further damage.

Look for a Clogged Condensate Drain Line

Your air conditioner naturally removes humidity from the air, which collects as water and exits through a condensate drain line. If this line becomes clogged with algae, dust, or debris, the water has nowhere to go. It will back up and overflow the drain pan, causing leaks near your indoor unit. If left unaddressed, this can lead to significant water damage to your ceilings, walls, and floors. This is more than a minor inconvenience; it’s a threat to your home that requires prompt attention.

Symptom: Strange Noises or Unpleasant Odors

Under normal conditions, your air conditioner should operate as quiet background noise. When new, loud, or unusual sounds suddenly appear, it’s a clear signal that something is wrong. Ignoring these auditory warnings can lead to more severe damage and expensive repairs. This is a critical step in ac troubleshooting that should not be overlooked.

Important: If you hear a loud mechanical sound like grinding, banging, or clanking, turn your AC system off immediately at the thermostat and the circuit breaker to prevent catastrophic failure.

Decoding Strange AC Noises

Your air conditioner often communicates problems through sound. Listening closely can help you identify the potential issue before calling a professional. Here are a few common sounds and what they typically mean:

• Banging or Clanking: This alarming sound often indicates a loose or broken part, such as a connecting rod, piston, or crankshaft inside the compressor. It could also be a displaced blower fan.
• Squealing or Screeching: A high-pitched squeal usually points to a failing belt or worn-out motor bearings in either the indoor blower or the outdoor condenser fan.
• Buzzing or Humming: While a low hum is normal, a loud, persistent buzzing is often a sign of an electrical issue. This could be a failing capacitor, a faulty contactor, or loose wiring.

Identifying Unpleasant Smells

Like noises, odors are another warning sign that requires prompt attention. If you notice any of these smells coming from your vents, it’s time to investigate.

• Musty or Moldy Smell: Often described as a “dirty sock” smell, this indicates the growth of mold or mildew on your unit’s evaporator coil or within the ductwork due to excess moisture.
• Burning Smell: A smell of burning plastic or wiring is a serious electrical fault. It could be an overheated motor or damaged wiring. Turn your system off at the breaker immediately.
• Rotten Egg Smell: This is a critical emergency. The smell of sulfur indicates a natural gas leak somewhere in your home that is entering your ductwork. Leave the house immediately and call your gas company from a safe location.

Your Next Step: Call for a Safety Inspection

When it comes to advanced ac troubleshooting for noises and smells, professional expertise is essential. These symptoms can point to serious mechanical and electrical failures that pose a safety risk. Our certified experts are equipped to diagnose these issues safely and provide a reliable solution. For your peace of mind, schedule a professional diagnosis today.

When to Stop Troubleshooting and Call a Professional

While basic ac troubleshooting can resolve many common comfort issues, the most important part of any DIY project is knowing when to stop. Your safety and the integrity of your HVAC system are paramount. Certain symptoms are clear indicators of a serious problem that requires the tools and expertise of a certified professional. Attempting to fix these issues yourself can be dangerous and often leads to more extensive and costly damage.

If you notice any of the following signs, put down the tools and pick up the phone. It’s the smartest and safest decision you can make.

The ‘Do Not Touch’ Checklist

These symptoms go beyond simple fixes and often point to a critical failure within your system. For your safety, call an expert immediately if you experience:

• Signs of a Refrigerant Leak: This includes visible ice or frost buildup on the copper lines of your condenser unit or a distinct hissing sound. Refrigerant is a hazardous material that should only be handled by a licensed technician.
• Loud Mechanical Noises: Grinding, squealing, or metallic banging sounds often indicate a failing motor, worn-out bearings, or a broken internal component. Continuing to run the unit can cause catastrophic failure.
• Burning Smells or Electrical Issues: Any odor resembling burning plastic or wiring is an immediate red flag for an electrical problem. If you see smoke or sparks, shut the system off at the breaker immediately.
• Repeatedly Tripping Breaker: If your AC unit’s circuit breaker trips more than once after you reset it, there is likely an electrical short or an overheating component that needs professional diagnosis.

Why Choose a Trusted Expert like RMI

Calling for service shouldn’t be a source of anxiety. When you call RMI, you’re choosing peace of mind. Our certified experts are trained to look beyond the immediate symptom to find and fix the root cause of the problem, ensuring a reliable, long-term solution. We respect your time, which is why our service vehicles arrive fully stocked with the most common parts and tools needed to complete repairs on the very first visit.

As a trusted Central Florida provider since 1999, we deliver cooling you can count on, with 24/7 emergency availability for when you need us most. Don’t let a serious AC issue disrupt your comfort or safety. Contact RMI today for professional service that gets the job done right, guaranteed.

Expert Help When DIY AC Troubleshooting Isn’t Enough

Armed with these tips, you can confidently tackle basic AC problems and potentially save yourself time and money. Simple steps, like checking your thermostat settings or replacing a clogged air filter, can often restore your comfort immediately. However, the most important part of any ac troubleshooting process is knowing when to stop. For complex issues involving electrical components, refrigerant leaks, or strange mechanical noises, it’s always safest to rely on a certified professional to prevent further damage.

If you’ve tried these steps and your home is still uncomfortably warm, don’t sweat it. As Central Florida’s trusted HVAC partner since 1999, the expert team at RMI HVACR is ready to help. Our 24/7 emergency service and fully stocked trucks mean we arrive prepared to deliver a fast, reliable solution. If your AC is still on the fritz, call our 24/7 emergency repair experts now! Let us restore your comfort so you can get back to enjoying your day.

Frequently Asked Questions

How often should I change my AC air filter?

For most homes, we recommend changing your AC air filter every 90 days. However, if you have pets, allergies, or live in a dusty area, changing it every 30-60 days is a better practice. A clean filter is crucial for efficient operation and good air quality. It prevents dust and debris from clogging your system, which is a simple step to avoid more complex issues and keep your unit running reliably all summer long.

What are the signs of a refrigerant (Freon) leak?

Common signs of a refrigerant leak include your AC blowing warm or lukewarm air, a hissing or bubbling sound near the unit, and visible ice buildup on the evaporator coils. You might also notice a sudden increase in your energy bills. Because handling refrigerant requires certified expertise and special tools, this is a problem that should always be addressed by a professional technician to ensure a safe and effective repair. Your safety is our top priority.

Why is my AC unit freezing up in the middle of summer?

An AC unit freezing up is typically caused by one of two issues: restricted airflow or low refrigerant. The most common culprit is a dirty air filter, which you can easily replace yourself. If a new filter doesn’t solve the problem, it likely indicates a refrigerant leak. This is a more complex issue that requires professional ac troubleshooting and repair from a certified expert to prevent damage to your compressor and restore reliable cooling.

How much does a typical AC repair service call cost?

The cost of a service call can vary, but most professional HVAC companies charge a diagnostic fee, typically ranging from $75 to $150, to identify the problem. The total repair cost will depend on the parts and labor required. Our certified technician will always provide a clear, upfront estimate for the full repair after the initial diagnosis, so you can make an informed decision before any work begins. Your comfort and trust are our priority.

Is it worth repairing an old AC unit or should I replace it?

Deciding between repair and replacement depends on the age of your unit and the cost of the repair. A good guideline is the “50% rule”: if a repair costs more than half the price of a new system, replacement is often the more reliable, long-term solution. For units over 10-15 years old that require frequent service, investing in a new, high-efficiency model will provide better performance and significant energy savings you can count on.

What is included in a professional AC maintenance visit?

A professional AC tune-up is a comprehensive inspection designed to keep your system running efficiently. Our expert technicians will clean the condenser and evaporator coils, check refrigerant levels, inspect all electrical connections, test the thermostat, and clear the condensate drain line. This preventative ac troubleshooting service helps catch small problems before they become major breakdowns, ensuring you have cooling you can depend on all season long.