How quickly can you respond to AC emergencies in Charleston?

We offer same-day service for AC emergencies in Charleston and surrounding areas. Our technicians understand the urgency of AC problems in South Carolina's hot, humid climate.

Do you work on historic homes in Charleston?

Yes, our technicians have extensive experience working on historic Charleston homes. We understand the unique challenges of retrofitting modern HVAC systems in older properties while preserving their character.

How does salt air affect AC systems in Charleston?

Salt air from the coast can cause corrosion on AC components. Our technicians are trained to identify and address salt air damage, and we recommend specific maintenance schedules for coastal properties.

What are common AC problems in Charleston homes?

Common issues include high humidity problems, salt air corrosion, refrigerant leaks, dirty coils from coastal conditions, and systems overworking due to Charleston's hot summers.

AC Repair Charleston SC | Historic Home Experts

A man in a polo shirt stands indoors, adjusting a switch on an open electrical panel while performing AC troubleshooting. The room features wooden floors and a hallway visible in the background.

My AC Won’t Turn On: Troubleshooting Before You Call a Technician

March 17, 2026 No Comments

My AC Won’t Turn On: Troubleshooting Before You Call a Technician When your AC system won’t turn on at all — no fan, no compressor, no response to thermostat changes — the cause is either an interruption in the electrical supply reaching the system (tripped breaker, blown fuse, safety switch activation, thermostat failure) or a failure of a startup component within the system itself (dead capacitor, burned contactor, failed control board, or seized compressor). About 30% of “AC won’t start” calls that Coastal Carolina Comfort responds to across South Carolina are resolved by the homeowner checks described below. The remaining 70% require professional diagnosis and repair. Coastal Carolina Comfort provides same-day diagnostic service for systems that won’t start across Summerville, Charleston, Columbia, and the entire Lowcountry and Midlands. Our NATE-certified technicians carry the common startup components — capacitors, contactors, control boards — needed to restore your system in a single visit. Call (843) 708-8735. Homeowner Troubleshooting: 6 Checks Before You Call These checks are safe for any homeowner to perform and take less than 10 minutes total. Work through them in order. Check 1: Thermostat Power and Settings Start at the thermostat — it’s the most common cause of a system that appears dead. Verify it has power. If the display is blank, the thermostat has lost power. Check whether it uses batteries (replace them) or is wired to the system (a tripped breaker or blown fuse at the air handler may have cut power to the thermostat). Verify the settings. Ensure the system is set to “cool” (not “off,” “heat,” or “fan only”), the set temperature is at least 3–5°F below the current room temperature, and any scheduling or away modes aren’t overriding your settings. Try a hard reset. Turn the thermostat completely off, wait 30 seconds, then turn it back to cooling mode. For smart thermostats, a power cycle or factory reset can resolve software glitches that prevent the system from responding. If the thermostat appears to be working correctly — display is on, settings are correct, it shows “cooling” — but the system doesn’t respond, the issue is downstream. Check 2: Circuit Breakers Your AC system typically uses two circuit breakers in your main electrical panel: one for the indoor air handler and one for the outdoor condenser unit. Check both. Look for a tripped breaker. A tripped breaker sits in the middle position — not fully “on” and not fully “off.” Push it firmly to “off” first, then back to “on.” If the breaker holds and the system starts, monitor it. If the breaker trips again within minutes, do not reset it a third time — the system has an electrical fault that requires professional diagnosis. Check for a blown fuse at the air handler. Some air handlers have a small fuse (typically 3–5 amp) on the control board that protects the low-voltage circuit. If this fuse blows, the thermostat loses its ability to communicate with the system. This fuse is accessible inside the air handler’s front panel — but if you’re not comfortable opening the panel, skip this check and call for service. Check 3: Emergency Shutoff Switch Many AC installations include a wall-mounted emergency shutoff switch that looks like a standard light switch — typically located near the indoor air handler or in the utility closet. If someone accidentally flipped this switch off (during maintenance, painting, or cleaning), the entire system is disabled. Check for a switch near the air handler that might be in the “off” position. Flip it on and see if the system responds. Check 4: Condensate Drain Safety Switch Many South Carolina HVAC installations include a float switch on the condensate drain line that shuts the system down when the drain line clogs and water backs up. This is a safety feature designed to prevent water damage — but it also means a simple drain clog can make your entire AC system unresponsive. If your system has a visible float switch on the drain line (a small device with a float attached to the PVC pipe near the air handler), check whether standing water is visible in the drain pan. If the pan is full, the float switch has activated. Clearing the drain line may restore system operation. Our guide on AC leaking water inside your house covers drain line clearing in detail. Check 5: Outdoor Disconnect Box Near your outdoor condenser unit, there’s a disconnect box — a small metal box mounted on the wall within a few feet of the unit. This box contains either a pull-out fuse block or a breaker that supplies power specifically to the outdoor unit. Check that the disconnect is in the “on” position and that the fuses (if applicable) haven’t blown. A blown disconnect fuse is a common cause of a system where the indoor fan runs but the outdoor unit doesn’t respond at all. Check 6: Wait 5 Minutes After Any Reset Modern AC systems have built-in time delays that prevent the compressor from restarting too quickly after a shutdown — rapid cycling can damage the compressor. If you’ve reset a breaker, flipped a switch, or changed the thermostat, wait at least 5 minutes before concluding the system isn’t responding. The delay is protecting your equipment. If the Homeowner Checks Don’t Work: Common Professional Repairs When all homeowner-accessible checks fail to restore the system, one of these mechanical or electrical failures is typically the cause. Failed Capacitor The run capacitor provides the electrical boost the compressor and fan motors need to start. When it fails, the motors can’t overcome their starting inertia. You might hear a clicking sound from the outdoor unit as the contactor engages, followed by a hum and then silence — the system is trying to start but the capacitor can’t deliver. Capacitor failure is the single most common reason an AC system won’t start. It’s also one of the most affordable repairs: $150–$300 including parts and labor. In South Carolina’s long cooling season, capacitors endure more

A close-up view of an air conditioner evaporator coil covered with a thick layer of ice and frost, indicating a malfunction or freezing issue.

AC Frozen Evaporator Coil: Why Your Air Conditioner Ices Up in Humid SC Weather

March 17, 2026 No Comments

AC Frozen Evaporator Coil: Why Your Air Conditioner Ices Up in Humid SC Weather A frozen evaporator coil occurs when the coil’s surface temperature drops below 32°F and moisture from your indoor air freezes on contact, building a layer of ice that blocks airflow and prevents heat absorption. The most common causes are restricted airflow from a clogged filter or dirty coil, low refrigerant charge from a leak, and blower motor failure that reduces air volume across the coil. In South Carolina’s high-humidity environment, frozen coils are both more common and more damaging than in drier climates — the heavy moisture content in Lowcountry and Midlands air means ice builds faster and produces more water when it melts. Coastal Carolina Comfort diagnoses and repairs frozen evaporator coils across Summerville, Charleston, Columbia, and all of South Carolina. Our NATE-certified technicians identify the root cause — not just thaw the ice — and provide upfront pricing before any repair begins. Call (843) 708-8735. How a Frozen Coil Damages Your AC System A frozen evaporator coil isn’t just a temporary inconvenience — it creates a cascade of problems that can damage multiple components if the system continues running. The compressor is at greatest risk. Under normal operation, liquid refrigerant enters the evaporator coil, absorbs heat, and exits as a gas before returning to the compressor. When the coil freezes, this heat exchange stops. Liquid refrigerant passes through the coil without vaporizing and reaches the compressor in liquid form. Compressors are designed to pump gas, not liquid. Liquid refrigerant entering the compressor — called liquid slugging — can crack valves, damage pistons, and cause catastrophic compressor failure. A compressor replacement typically costs $1,500–$3,000+. Water damage when the ice melts. A frozen coil accumulates a surprising amount of ice. When the system shuts off or the ice begins to melt, the resulting water can easily overwhelm the drain pan — especially if the drain line is also partially clogged (a common combination in South Carolina). Water overflows onto floors, into ceilings, or through walls. Read our guide on AC leaking water inside your house for immediate steps if you’re already dealing with water. Reduced system life. Repeated freeze-thaw cycles stress the coil fins, degrade the coil’s protective coating, and can eventually cause refrigerant leaks in the coil itself — one of the most expensive AC repairs. The 5 Causes of Frozen Evaporator Coils in South Carolina 1. Clogged Air Filter This is the most common cause — and the most preventable. A clogged filter restricts the volume of warm air passing over the evaporator coil. Without sufficient warm air, the coil’s temperature drops below the freezing point. Moisture in the air freezes on contact, and the ice layer further restricts airflow, accelerating the freeze. In South Carolina, where pet dander, pollen, dust, and high humidity all contribute to faster filter loading, a filter that might last 90 days in a drier climate may need replacement every 30 days during peak cooling season. The fix: Replace the filter, turn the system off for 2–3 hours to allow complete thawing, then restart. If the system runs normally and doesn’t refreeze, the filter was the sole cause. If ice returns within 24 hours, there’s an additional underlying issue. 2. Low Refrigerant From a Leak Low refrigerant charge causes the evaporator coil’s temperature to drop below normal operating range. When the coil is too cold, moisture freezes on its surface instead of condensing into liquid and draining away. The ice insulates the coil, making it even colder, and the freeze accelerates until the coil is completely encased. This is the most common mechanical cause of frozen coils, and it requires professional repair. A technician will thaw the coil, test for leaks, repair the leak source, and recharge the system to manufacturer specifications. Simply adding refrigerant without fixing the leak guarantees the problem will return. In South Carolina’s coastal environment, refrigerant line corrosion from salt air is a significant contributor to leaks — particularly on homes within a few miles of Charleston Harbor, James Island, or the Isle of Palms. 3. Dirty Evaporator Coil Even with regular filter changes, the evaporator coil accumulates dust, biological growth, and particulate matter over time — especially in South Carolina’s humid environment where mold and mildew thrive on the constantly damp coil surface. A dirty coil insulates itself from the warm air passing over it. The coil can’t absorb enough heat, its temperature drops, and the same freeze cycle begins. The difference is that a dirty-coil freeze develops more gradually than a low-refrigerant freeze — you might notice declining performance for weeks before ice becomes visible. The fix: Professional coil cleaning. This requires access to the indoor unit, coil-specific cleaning solution, and careful handling to avoid damaging the delicate aluminum fins. Coil cleaning is typically included in comprehensive maintenance visits that prevent frozen coils and costs $150–$300 as a standalone service. 4. Blower Motor Failure or Reduction The blower motor moves air across the evaporator coil. If it fails entirely, airflow stops completely and the coil freezes rapidly. A partially failing motor — running at reduced speed due to worn bearings, a failing capacitor, or a winding issue — moves insufficient air, causing a slower but equally damaging freeze. In multi-speed systems, a motor stuck on low speed may provide enough airflow for mild days but insufficient volume on high-demand days, creating intermittent freezing that’s harder to diagnose. 5. Collapsed or Blocked Return Ductwork If the return duct — the large duct that carries warm room air back to the air handler — is crushed, disconnected, or severely blocked, the volume of air reaching the evaporator coil drops below the minimum threshold. This can happen when stored items are placed on flex duct in an attic, when a duct joint separates due to age or poor installation, or when a return vent is blocked by furniture or closed. This cause is more common in homes with ductwork routed through attics — a standard

A person wearing gray socks stands near an AC water problem, with a puddle forming under a leaking HVAC unit in a utility room. The unit’s panel is open and cleaning supplies are visible in the background.

Why Is My AC Leaking Water Inside My House?

March 17, 2026 No Comments

Why Is My AC Leaking Water Inside My House? Water pooling around your indoor AC unit is almost always caused by a clogged condensate drain line, a cracked or overflowing drain pan, or a frozen evaporator coil that’s melting faster than the drainage system can handle. In South Carolina’s high-humidity climate, your AC removes significantly more moisture from the air than systems in drier regions — often producing 5–20 gallons of condensate per day during peak summer. That volume of water needs a clear path out of your home, and when anything blocks or breaks that path, the water ends up on your floors. Coastal Carolina Comfort diagnoses and repairs AC water leaks across Summerville, Charleston, Columbia, and the entire South Carolina Lowcountry and Midlands. Most condensate-related repairs are completed in a single same-day visit. Call (843) 708-8735. Why South Carolina Homes See More AC Water Leaks Understanding why this problem is so common in our region starts with understanding how much moisture your AC handles. A residential air conditioning system in South Carolina processes far more humidity than the same system would in Colorado, Arizona, or even the mid-Atlantic states. When warm, humid Lowcountry or Midlands air passes over the cold evaporator coil, moisture condenses on the coil’s surface — the same way water beads on a cold glass on a summer day. That condensation collects in a drain pan below the coil and flows through a drain line to the outside of your home. During a typical South Carolina summer day with 80%+ relative humidity, your system may remove 5–20 gallons of water from your indoor air. That’s a tremendous amount of water flowing through a ¾-inch PVC pipe every day for six months. The warm, wet environment inside that drain line is ideal for algae, mold, and bacterial growth — which is exactly what clogs it. This is why AC water leaks are one of the most common repair calls Coastal Carolina Comfort receives across the region, and why regular AC maintenance that includes drain line treatment is so important here. The 5 Most Common Causes of AC Water Leaks 1. Clogged Condensate Drain Line This is the cause in roughly 70% of AC water leak calls we respond to across South Carolina. The drain line — typically a ¾-inch PVC pipe running from the drain pan to an exterior exit point — becomes blocked by algae, mold, rust, or mineral deposits. Water backs up behind the clog, fills the drain pan, and overflows onto your floors. South Carolina’s humidity makes drain clogs far more common than in drier climates because the warm, constantly wet interior of the drain line is a perfect incubator for biological growth. In the Lowcountry, we see drain lines that clog within 3–6 months of cleaning if no preventive treatment is applied. The fix: A technician clears the clog using a wet/dry vacuum, nitrogen flush, or manual snake, then treats the line with an algaecide tablet or solution to inhibit regrowth. This is one of the most affordable AC repairs — typically $100–$200. The best prevention is flushing the drain line with vinegar monthly during cooling season and scheduling professional treatment during your annual maintenance visit. 2. Cracked or Rusted Drain Pan The drain pan sits beneath the evaporator coil and catches condensation before it reaches the drain line. Over time — especially in the high-moisture environment inside a South Carolina air handler — metal drain pans rust through and plastic pans can crack. When the pan is compromised, water bypasses the drain line entirely and drips directly onto the floor, into the ceiling, or into the crawl space below. The fix: Drain pan replacement. Secondary drain pans (the backup pan beneath the air handler) are accessible and relatively inexpensive to replace. Primary drain pans (integrated into the coil assembly) are more involved and may require partial disassembly of the air handler. Costs typically range from $200–$600 depending on accessibility and pan type. 3. Frozen Evaporator Coil Melting When the evaporator coil freezes — due to low refrigerant, restricted airflow, or a blower motor failure — the ice buildup can be substantial. When the system shuts off or the ice begins to melt, the volume of water released can overwhelm the drain pan and flood the area around the unit. This is different from a normal condensate leak because the water volume is much larger and more sudden. If you see ice on the indoor unit or the copper refrigerant lines, you’re dealing with a coil freeze — not a simple drain clog. Read our complete guide on frozen evaporator coils in humid South Carolina weather. The fix: Turn the system off to allow the coil to thaw completely (2–3 hours minimum). Place towels or a shallow pan to catch the meltwater. Then call for professional diagnosis to identify why the coil froze in the first place — the freeze is a symptom, not the root cause. 4. Disconnected or Damaged Drain Line The PVC drain line can become disconnected from the drain pan fitting, cracked from physical impact, or separated at a joint due to poor installation or settling of the home. When this happens, condensate exits the system but misses the drain path — flowing instead into ceilings, walls, or onto floors at the point of disconnection. This is more common in homes where the air handler is located in the attic — found frequently across Charleston, Summerville, and Columbia — because the drain line has a longer run and more joints that can separate over time. The fix: Reattach, reseal, or replace the damaged drain line section. This is typically a straightforward repair costing $100–$300 depending on accessibility and the extent of the damage. 5. Condensate Pump Failure Some AC installations — particularly where the air handler is in a basement, crawl space, or interior closet below the level of the exterior drain exit — use a condensate pump to move water uphill to an exit point. When

A smart thermostat is mounted on a beige wall in a South Carolina hallway, displaying 74°F. Sunlight streams through an open doorway, brightening the space—ideal for spotting AC short cycling and learning its causes and fixes.

AC Keeps Turning On and Off: Short Cycling Causes and Fixes in South Carolina

March 17, 2026 No Comments

AC Keeps Turning On and Off: Short Cycling Causes and Fixes in South Carolina Short cycling is when your air conditioning system turns on, runs for only a few minutes (typically 2–8 minutes instead of the normal 10–20 minute cycle), shuts off, and then starts again shortly after. This pattern repeats continuously without the system ever completing a full cooling cycle. The most common causes are an oversized AC system, a failing compressor or capacitor, a refrigerant leak that’s triggering low-pressure safety shutoffs, or a thermostat malfunction. Short cycling isn’t just an annoyance — it’s one of the most damaging conditions for your air conditioning system. Coastal Carolina Comfort diagnoses short cycling across Summerville, Charleston, Columbia, and every community we serve in the South Carolina Lowcountry and Midlands. Call (843) 708-8735 for a same-day diagnostic. Why Short Cycling Damages Your AC System Every time your compressor starts, it draws significantly more electrical current than during steady operation — typically 4–8 times its running amperage. In a normal cycle, this startup surge happens a few times per hour. In a short-cycling system, the compressor may start and stop 10–15 times per hour, each time drawing that heavy startup current. This repeated electrical stress overheats the compressor windings, weakens the capacitor faster, increases wear on the contactor, and spikes your energy bills — all while failing to actually cool your home because the system never runs long enough to complete a full cooling cycle. In South Carolina’s climate, where the cooling season runs from April through October, short cycling compounds damage faster than in regions with shorter summers. Six months of short cycling can take years off a compressor’s life. The 7 Most Common Causes of AC Short Cycling 1. Oversized AC System This is the most common cause of chronic short cycling — and the hardest to fix because it’s a design problem, not a component failure. An oversized AC system cools the air near the thermostat quickly but shuts off before it has time to properly cool the rest of the home or adequately remove humidity. Minutes later, the temperature near the thermostat rises again, the system kicks back on, cools briefly, shuts off — and the cycle repeats. In South Carolina, oversized systems create a particularly unpleasant result: the home may reach the set temperature on the thermostat but feel clammy and uncomfortable because the short run times don’t allow the evaporator coil to remove enough moisture from the air. A house at 72°F with 65% indoor humidity feels warmer and stickier than a house at 74°F with 50% humidity. Oversized systems are distressingly common in South Carolina new construction — particularly in Summerville’s Nexton and Cane Bay communities, Lexington’s newer subdivisions, and Daniel Island and Mount Pleasant developments — where builder-grade installations may prioritize cost or use rule-of-thumb sizing rather than Manual J load calculations. The fix for an oversized system is either replacement with a correctly sized unit or, in some cases, installation of a variable-speed system that can modulate its output to match the actual load. 2. Failing or Failed Capacitor A weakening run capacitor can’t deliver sufficient electrical energy to keep the compressor running through a full cycle. The compressor starts, draws heavily on the failing capacitor, and the capacitor’s voltage drops below the threshold — causing the compressor to shut down on an overcurrent safety. The capacitor partially recovers during the off-cycle, the system tries again, and the pattern repeats. This is one of the most common and most affordable AC repairs — typically $150–$300. It’s also one of the easiest to prevent through regular AC maintenance, which includes testing capacitor health before the component fails. 3. Low Refrigerant Triggering Safety Shutoffs When refrigerant levels drop below a certain threshold, the system’s low-pressure safety switch activates and shuts down the compressor to prevent damage. As the system sits idle, pressures equalize enough for the safety switch to reset. The system starts again, runs until pressures drop, and shuts off again — creating a short cycling pattern. Low refrigerant always means a leak. Simply adding refrigerant without repairing the leak creates a recurring problem that worsens as the leak grows. In South Carolina’s humid environment, running a low-charge system also risks freezing the evaporator coil — adding another layer of problems. 4. Frozen Evaporator Coil Ice buildup on the evaporator coil restricts airflow and disrupts the heat exchange process. As ice accumulates, the system’s safety mechanisms may shut it down. The system restarts after partial thawing, runs until ice rebuilds, and shuts down again. In South Carolina’s humidity, a frozen coil is especially problematic because the melting ice produces heavy condensation that can overwhelm the drain pan and flood floors. If you see ice on the indoor unit and your system is short cycling, turn the system off for 2–3 hours to allow complete thawing before calling for diagnosis. 5. Thermostat Malfunction A thermostat with a faulty temperature sensor, dead battery in a wireless sensor, or improper placement can send erratic signals to the system. If the thermostat oscillates between readings — sensing 73°F one minute and 76°F the next — the system responds by cycling on and off in rapid succession. Smart thermostats with multiple sensors, learning algorithms, and Wi-Fi connectivity have more potential failure points than simple programmable models. If short cycling started after a thermostat change or firmware update, the thermostat itself is the likely culprit. 6. Dirty or Blocked Condenser Coil When the outdoor condenser coil can’t release heat effectively — due to dirt buildup, pollen coating, or vegetation growing too close — the system’s high-pressure safety switch can activate and shut down the compressor. After the system cools down briefly, it restarts and the cycle continues. Keeping vegetation cleared 2 feet from the outdoor unit and scheduling annual coil cleaning prevents this cause entirely. 7. Compressor Overheating A compressor that’s failing internally — due to worn bearings, valve leaks, or electrical winding degradation — generates excessive heat during operation.

A man in a gray polo shirt inspects an outdoor AC unit for strange AC sounds in a backyard next to a brick house, surrounded by green plants and grass.

AC Unit Making Strange Noises: What Each Sound Means and When to Call for Repair

March 17, 2026 No Comments

AC Unit Making Strange Noises: What Each Sound Means and When to Call for Repair A healthy air conditioning system produces a consistent, low-level hum during operation. When you hear new sounds — grinding, buzzing, clicking, banging, hissing, or screeching — each noise points to a specific mechanical or electrical problem. Identifying what the sound is and where it’s coming from helps determine whether you need immediate service, can schedule a repair within a few days, or simply have a minor issue that’s easy to resolve. Coastal Carolina Comfort’s NATE-certified technicians diagnose and repair noisy AC systems across Summerville, Charleston, Columbia, and the entire South Carolina Lowcountry and Midlands. We identify the source of the sound, explain what’s causing it, and provide upfront pricing before any work begins. Call (843) 708-8735. A Sound-by-Sound Diagnostic Guide Grinding: Failing Motor Bearings What it sounds like: A metallic grinding, scraping, or growling that gets louder over time. It may be intermittent at first and become constant. Where it comes from: Usually the indoor blower motor or the outdoor condenser fan motor. What’s happening: The motor bearings that allow the shaft to spin freely are wearing out. As the bearings degrade, metal contacts metal, creating the grinding sound. Eventually the motor seizes completely — which turns a $350–$700 motor replacement into a potential compressor failure if the system overheats. Urgency level: Schedule within 1–3 days. A grinding motor can fail at any time. Continuing to run the system accelerates the damage but won’t cause an immediate safety hazard. The longer you wait, the higher the chance the motor seizes during a peak-heat day when you need it most. South Carolina note: The extended cooling season in the Lowcountry and Midlands puts more annual hours on motor bearings than most of the country. A motor that might last 15 years in a cooler climate may wear out in 10–12 years here because it runs 6+ months per year. Buzzing: Electrical Problems What it sounds like: A steady electrical buzz or hum, louder than the system’s normal operating sound. May come from the outdoor unit, indoor unit, or both. What’s happening: Buzzing from the outdoor unit most commonly indicates a failing contactor (the electrical relay that starts the compressor) or loose wiring connections vibrating during operation. Buzzing from the indoor unit may point to a failing transformer, a relay issue, or a blower motor with electrical problems. Urgency level: Schedule within 1–2 days. Electrical issues can worsen without warning. A contactor that’s arcing or buzzing can weld itself shut (causing the system to run nonstop), fail open (causing a complete shutdown), or create a fire risk if left unaddressed. If the buzzing is accompanied by a burning smell, turn the system off at the breaker and call for emergency AC repair in the Lowcountry. Clicking: Capacitor or Control Board Issues What it sounds like: Repeated clicking sounds at startup — the system tries to start, clicks, pauses, tries again, clicks. Or a single click followed by silence instead of the compressor engaging. What’s happening: This is typically a failed run capacitor trying and failing to deliver the electrical boost the compressor needs to start. The click is the contactor engaging, but without sufficient capacitance, the compressor can’t turn over. The system tries repeatedly, clicking each time. Less commonly, clicking indicates a control board relay failure — the electronic brain of the system is sending the start signal but a relay on the board isn’t completing the circuit. Urgency level: Same-day to next-day. The system won’t cool in this state. If the weather is mild, next-day service is fine. In South Carolina summer heat, this is a same-day call. A failed capacitor is one of the quickest and most affordable repairs — typically $150–$300 including parts and labor. Banging or Clanking: Loose or Broken Internal Components What it sounds like: A rhythmic banging, clanking, or knocking — usually from the outdoor unit. The sound follows the fan’s rotation cycle. What’s happening: Something inside the unit is loose and making contact with a moving part. The most common causes are a broken fan blade striking the housing, a loose compressor mounting bolt allowing the compressor to vibrate excessively, or debris (a stick, acorn, or small animal) caught inside the condenser housing. Urgency level: Turn off and schedule same-day. A broken fan blade or loose component can cause escalating damage to other parts with every rotation. Turn the system off at the thermostat and call for service. Do not reach inside the unit to investigate. Hissing or Bubbling: Refrigerant Leak What it sounds like: A persistent hiss from the indoor or outdoor unit, or a bubbling/gurgling sound from the refrigerant lines. What’s happening: Refrigerant is escaping through a hole or crack in the copper lines, coil, or fittings. A hiss indicates gas-phase refrigerant escaping under pressure. A bubbling sound indicates the leak is in a section where refrigerant is in liquid phase. Urgency level: Schedule within 1–2 days. A refrigerant leak won’t cause immediate damage to your home, but every day it leaks reduces cooling capacity and forces the compressor to work harder. Running a system with critically low refrigerant can cause compressor damage. If you also notice ice forming on the indoor unit, turn the system off. In South Carolina’s coastal and humid environment, refrigerant line corrosion is more common than in drier climates — particularly on homes near the coast where salt air accelerates copper degradation. Our guide on what South Carolina humidity does to your cooling system explains why. Screeching or Squealing: Belt or Motor Issues What it sounds like: A high-pitched screech or squeal, usually at startup, that may fade as the system reaches operating speed. What’s happening: In older systems with belt-driven blower motors, a worn or misaligned belt slips and squeals — similar to a car’s serpentine belt. In newer direct-drive systems, the screech may indicate a failing motor bearing or a blower wheel rubbing against its housing. Urgency level: Schedule within

A man in a living room adjusts a wall-mounted thermostat, which displays 84°F—hinting at AC not cooling. Sunlight streams through large windows, and family photos hang on the wall behind him.

Why Is My AC Running But Not Cooling the House?

March 17, 2026 No Comments

Why Is My AC Running But Not Cooling the House? When your AC runs continuously but your home isn’t reaching the set temperature, the system is either failing to produce adequate cooling or losing that cooling before it reaches your living spaces. The most common causes are low refrigerant charge from a leak, a dirty evaporator or condenser coil restricting heat transfer, leaking ductwork that dumps conditioned air into unconditioned spaces, or a system that is undersized for your home’s actual cooling load. Coastal Carolina Comfort diagnoses why your AC isn’t cooling effectively across Summerville, Charleston, Columbia, and every community we serve in the South Carolina Lowcountry and Midlands. Our NATE-certified technicians identify the root cause — not just the symptom — and provide upfront pricing before any repair begins. Call (843) 708-8735. First: Understanding the Difference Between “Not Cooling” and “Blowing Warm Air” These two problems overlap but aren’t identical, and the distinction affects the diagnostic path. AC blowing warm air means the air from your vents is noticeably warm — room temperature or warmer. This typically points to a complete failure of the cooling cycle: dead compressor, severely depleted refrigerant, tripped outdoor breaker, or a heat pump stuck in heating mode. If this describes your situation, our guide on AC blowing warm air covers those specific causes. AC running but not cooling means the system produces some cool air — you can feel it at the vent — but your home never reaches the set temperature, or takes far too long to get there. The system runs for hours without cycling off. This is a subtler problem with a wider range of possible causes, and it’s what this article addresses. In South Carolina’s climate, the distinction matters more than in cooler regions. A system that’s “almost cooling” but falls 5°F short can leave your home at 80°F with 70% humidity — which feels miserable even though the AC is technically doing something. The 7 Most Common Reasons Your AC Runs But Doesn’t Cool 1. Dirty Condenser Coil (Outdoor Unit) The condenser coil is where your system releases the heat it absorbed from inside your home. When the coil’s aluminum fins become coated with dirt, pollen, grass clippings, or pet hair, heat transfer drops dramatically. Your system still runs — the compressor works, the fan spins, cool air reaches the vents — but the system can’t reject enough heat to keep up with the load. In South Carolina, condenser coils take a beating. Spring pollen coats them heavily by April. Summer storms blow debris into the fins. And the combination of heat and humidity creates ideal conditions for biological growth between the fins. This is one of the most common — and most fixable — reasons an AC runs all day without cooling adequately. A professional coil cleaning restores heat transfer capacity and is typically included in regular maintenance that prevents costly repairs. 2. Dirty or Restricted Evaporator Coil (Indoor Unit) The evaporator coil absorbs heat from your indoor air. When it becomes coated with dust, mold, or biological growth — which happens faster in South Carolina’s humidity than in drier climates — its ability to absorb heat decreases. The air passing over a dirty evaporator coil cools less effectively, which means the air reaching your vents is cooler than room temperature but not cold enough to overcome the heat gain in your home. A dirty evaporator coil also increases humidity in your home because the coil can’t properly dehumidify the air passing over it. This is why a home might be at 74°F but feel clammy and uncomfortable — the AC is partially cooling but failing to adequately remove moisture. Learn more about what South Carolina humidity does to your cooling system. 3. Low Refrigerant Charge A partially depleted refrigerant charge produces exactly this symptom — the system runs, cool air reaches the vents, but the cooling capacity isn’t enough to match the heat load. Unlike a completely empty system (which blows warm air), a slow leak creates a gradual decline in performance that homeowners often attribute to “the system getting old” or “it’s just really hot outside.” The temperature differential between the supply air and return air tells the story. A properly charged system in South Carolina should produce a 15–20°F differential. If your supply air is only 8–12°F cooler than your return air, low refrigerant is a prime suspect. 4. Ductwork Leaks This is the hidden culprit that no amount of AC repair will fix, because the AC itself is working correctly. If your ductwork has gaps, disconnected joints, or deteriorated flex connections — especially where it runs through an unconditioned attic — cooled air escapes before it reaches your rooms. In a Lowcountry attic during summer, ambient temperatures regularly exceed 140°F. A duct leak in that environment doesn’t just lose cooled air — it actively pulls superheated attic air into the duct system, warming the conditioned air as it travels to your vents. Ductwork problems are especially common in older homes across Summerville’s Historic District, Charleston’s peninsula, and Columbia’s Shandon and Forest Acres neighborhoods where original ductwork may be 30–50+ years old. 5. Undersized or Improperly Sized System If your AC system was sized incorrectly for your home’s actual cooling load, it will run continuously on hot days without ever reaching the set temperature. This is more common than you’d expect, particularly in South Carolina where cooling loads are exceptionally high. An undersized system literally cannot produce enough cooling capacity to overcome the heat gain from walls, windows, attic, and South Carolina’s relentless humidity. Oversized systems create a different problem — short cycling — but undersized systems simply run all day, every day, wearing themselves out faster and costing more to operate. Sizing problems are especially prevalent in new construction where builder-grade systems may have been selected for cost rather than performance, and in homes that have been renovated or had additions built without upgrading the HVAC system to match the increased square footage.

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