View source for AC Not Cooling After Refrigerant Recharge: What Went Wrong

<html><p> <img  src="https://seo-neo-client.s3.us-east-1.amazonaws.com/airpro-heating-cooling/hvac%20system%20repair.png" style="max-width:500px;height:auto;" ></img></p><p> Air conditioners rarely stop cooling out of the blue. When they do, low refrigerant is often blamed, and a quick recharge sounds like the cure. Then the system still blows lukewarm air, or cools for a day and slides back to tepid. I’ve been called to dozens of homes and small offices right after a “top-off” that didn’t fix the problem. The pattern is consistent: recharging treats a symptom, not the disease. To get lasting cold air, you need to understand what actually failed and why the numbers on a gauge set don’t tell the whole story.</p> <p> This is a walk-through of what typically goes wrong, how to separate a simple fix from a layered problem, and when it’s better to repair than to keep feeding refrigerant into a leaking system. Along the way we’ll touch on thermostat misreads, airflow mistakes, non-condensables in a system, and even situations where the AC is fine but the house is the issue.</p> <h2> Why a recharge didn’t restore cooling</h2> <p> Refrigerant doesn’t get used up. If the system needed a recharge, it lost charge somewhere. A well-installed and maintained system can run a decade or more without needing to add refrigerant. When you have to add it, you should ask where it went.</p> <p> A basic top-off can briefly mask a leak. Pressure and temperatures look normal for a while, the supply vents feel cooler, and everyone breathes a sigh of relief. But if the leak remains, the cooling fades again. Worse, if air or moisture got into the lines during prior low-charge operation or an improper service, your AC’s performance can be compromised even at a “correct” charge. Moisture reacts with oil and refrigerant to form acids, and air displaces refrigerant and skews pressures. These contaminants can make an otherwise healthy compressor noisy, sluggish, or short-lived.</p> <p> I’ve seen a different failure as well: the system was never undercharged. The root cause was airflow, controls, or coil cleanliness. In those cases, adding refrigerant makes performance worse by pushing the system out of design balance.</p> <h2> The charging method matters</h2> <p> A tech can add refrigerant several ways. Each method has its place, but each can mislead if applied blindly.</p> <ul>  <li> <p> Superheat method: Used for fixed orifice systems like piston or capillary tube metering devices. You adjust charge to achieve a target superheat based on indoor wet-bulb and outdoor dry-bulb measurements. If airflow or indoor load is wrong, the target calculation becomes meaningless.</p></li> <li> <p> Subcooling method: Used for systems with a TXV. You charge to a target subcooling specified by the manufacturer. This requires accurate line temperature and liquid pressure readings and assumes the condenser coil is clean and airflow across it is correct. Debris or matted fins will force high head pressure and fake a “low charge” look.</p></li> <li> <p> Weigh-in: The most reliable after a full evacuation when all refrigerant was recovered. You add the factory-specified amount for the line set length, then verify with subcooling/superheat. If no one recovered, evacuated, and weighed in, the term “recharge” likely means guesswork.</p></li> </ul> <p> If the AC is not cooling after a recharge, I ask whether the tech used superheat or subcooling correctly, measured indoor and outdoor conditions, verified metering device type, and documented the numbers. A scribbled “added 2 pounds” on the invoice without temperatures and pressures often precedes a callback.</p> <h2> Leaks are common, but not all leaks are equal</h2> <p> Finding and fixing leaks is the most common resolution. The location and size of the leak determine your next steps.</p> <p> The evaporator coil inside the air handler is a frequent culprit. In homes with cats, dogs, or carpeting, fine dust and dander cling to the coil, trap moisture, and create a mildly corrosive film. After a few years, pinholes appear. Small leaks can be elusive: dye injection may help, but ultraviolet dye risks contaminating oil and is not my first choice. I prefer a high-quality electronic leak detector paired with pressurizing the system using nitrogen and a trace of refrigerant. You listen, sniff, and soap-solution suspect joints. If the leak is tiny, you may need to isolate the coil and test it alone.</p> <p> Outdoor coils leak less often, but they do fail near the U-bends and at factory brazed joints. Line sets can leak at flare or brazed connections, or where they rub on a roof edge or attic truss. I once found a pinhole under a saddle clamp in a crawlspace that had been rubbing for years, invisible until we stripped the insulation <a href="https://tango-wiki.win/index.php/Heater_Not_Working_with_Heat_Pump_Systems:_Defrost_and_Balance_Tips"><strong>professional hvac repair</strong></a> and saw the greenish oil stain.</p> <p> When a leak is found and repaired, the system must be evacuated to 500 microns or better and verified with a decay test. Skipping the deep vacuum allows moisture to remain, which can freeze in the metering device and cause erratic cooling. If your system was just “topped off” without repair and evacuation, that explains why it cools briefly and quits.</p> <h2> Airflow is the silent saboteur</h2> <p> A refrigeration circuit expects a certain volume of air across the evaporator and condenser. Too little air and coil temperatures swing to extremes. Frost or even ice can form on the indoor coil, blocking airflow further and turning the system into a self-choking loop. On the outdoor side, poor airflow drives head pressure up and can cause the compressor to overheat. Both situations can make “ac not cooling” feel like a charge problem when it’s actually an airflow problem.</p> <p> Filters are the first check. I’ve pulled out pleated filters with a MERV rating far too high for the blower, practically a felt blanket. Good filtration matters, but a high-resistance filter chokes airflow unless the ductwork and blower are sized to match. Dirty evaporator coils act like a clogged filter you can’t see. If the technician didn’t open the air handler and inspect the coil, they might have missed the main constraint.</p> <p> Ductwork design can be a culprit. Flex ducts that snake around joists with tight bends, collapsed inner liners, disconnected returns, or supply trunks undersized for the system tonnage will rob your AC of performance. I had a 3-ton condenser paired with a duct system that could barely support 900 CFM. The result was a cold evaporator, sweating ducts, and short-lived compressors. No amount of refrigerant would fix that mismatch.</p> <p> Finally, blower speed settings matter. After a coil cleaning, some systems need a blower tap increase to hit the right CFM per ton. If your furnace not heating well in winter required slower blower settings for quieter heat, those settings may be wrong for summer AC.</p> <h2> Non-condensables and moisture inside the system</h2> <p> If your AC was run for a long period with very low charge, or it was serviced without proper evacuation, the system may have air or moisture inside. Air in the lines increases head pressure, reduces subcooling, and starves the evaporator, all while the liquid line might feel misleadingly warm. Moisture can freeze in the TXV or capillary tube, creating intermittent cooling: fine for ten minutes, then warm as ice chokes refrigerant flow.</p> <p> When I see odd pressure-temperature relationships, unstable superheat, or a system that behaves differently minute to minute, I suspect non-condensables or moisture. The fix is not another recharge. It’s a full recovery, filter-drier replacement, deep vacuum with a good micron gauge, and a proper weigh-in. Many calls that start with “ac not cooling after recharge” end with replacing a moisture-saturated drier and doing the job by the book.</p> <h2> The metering device: TXV, EEV, or fixed orifice</h2> <p> Your metering device controls refrigerant flow into the evaporator. If it sticks or fails, the evaporator starves or floods, and the system will not cool correctly, no matter how much refrigerant you add.</p> <p> TXVs fail in two common ways. They stick due to contamination or lose their bulb charge. A dead bulb drives the valve wide open or locked shut depending on design. If the bulb isn’t well strapped and insulated to the suction line, the valve reads the wrong temperature and meters poorly. Technicians sometimes misdiagnose a starved evaporator as low charge when it’s a TXV issue. On fixed orifice systems, a plugged screen at the orifice or a fragment of Teflon tape lodged inside can mimic the same symptoms.</p> <p> Modern systems with electronic expansion valves are less common in small residential units but show up in higher-end equipment. A weak step motor or control board fault can confuse diagnostics. If your system has an EEV, a simple recharge won’t be the solution to erratic cooling.</p> <h2> Thermostat and control logic missteps</h2> <p> A thermostat off by two or three degrees can gloss over a cooling issue or create phantom complaints. More often, though, the problem is staging or fan control. On two-stage systems, if stage two never kicks on due to a loose low-voltage connection or a flawed configuration, you only get part of the capacity. Likewise, if the thermostat set the fan to circulate intermittently, it may blow warm air between cycles, giving the impression the AC is not cooling even when the coil is fine.</p> <p> Homeowners sometimes replace thermostats but leave old, brittle wiring in the wall. I’ve found intermittent open circuits on a damp summer day that worked again when the wall dried. Those gremlins are easy to misread as refrigerant problems.</p> <h2> The compressor and its support cast</h2> <p> Compressors are tougher than people think, but they do fail. They also suffer from external problems that make them look bad. If a scroll compressor runs for long periods undercharged, it can overheat and lose efficiency. If liquid refrigerant floods back due to poor charge or TXV issues, it can damage valves. A compressor with worn valves will show low head pressure and low suction, and it won’t move sufficient refrigerant even with a proper charge.</p> <p> Supporting hardware matters. A weak run capacitor can make the compressor slow to start, stall, or short cycle. A failing condenser fan motor lets head pressure climb. High pressure trips will shut the system down until it cools, again presenting as inconsistent cooling. Inspectors who only check refrigerant and not electrical readings miss these simple but decisive faults.</p> <h2> When the house is the problem</h2> <p> Sometimes the AC does its job, but the building beats it. A sun-blasted bonus room over a garage with R-13 in the knee walls and recessed lights leaking air can overwhelm a correctly charged 3-ton system. If the attic sits at 130 degrees and the ducts run through it uninsulated or with gaps, you lose a lot of capacity before the air reaches you. Leaky returns can pull hot attic air into the system, loading the coil beyond what the design anticipated.</p> <p> I’ve measured houses that need 20 to 30 percent more cooling on a 100-degree afternoon than a standard load calculation predicted, all because of infiltration and radiant gains. In those homes, “ac not cooling” is not the same as “refrigerant problem.” Better duct sealing, attic insulation, and shading can reduce complaints more than an ounce of refrigerant ever will.</p> <h2> Good diagnostics beat guesswork</h2> <p> A systematic approach avoids repeated recharges and callbacks. Here is a concise, reality-tested sequence that pairs with a technician’s visit and a homeowner’s observations.</p> <ul>  <li> <p> Visual and airflow checks: Confirm filter condition, evaporator coil cleanliness, blower operation, and condenser coil cleanliness. Verify all fans run and rotate the right direction. Measure static pressure and confirm airflow is within range for the system tonnage.</p></li> <li> <p> Electrical health: Test capacitors under load, inspect contactors, verify voltage at the condenser and air handler, and ensure control wiring is secure.</p></li> <li> <p> Refrigeration readings: Identify the metering device, then measure superheat and subcooling against target values, not just pressures. Compare suction line temperature, liquid line temperature, and line set insulation condition.</p></li> <li> <p> Leak test if low: If charge is low, recover, nitrogen pressure test with a trace gas, locate and repair the leak, then evacuate to under 500 microns with a decay test. Replace filter-drier. Weigh in the correct charge and confirm performance.</p></li> <li> <p> Verify load and distribution: Check supply and return temperatures, room-to-room delivery, and duct integrity. Look for signs of duct leakage and attic heat issues.</p></li> </ul> <p> That sequence prevents chasing the wrong rabbit and keeps your hvac system lifespan from being shortened by band-aid fixes that stress the compressor and motors.</p> <h2> Edge cases that fool the gauge set</h2> <p> A few repeat offenders deserve mention because they trip up even experienced techs.</p> <p> A partially frozen coil can show low suction pressure that looks like low charge. If you don’t let the coil thaw fully and restore airflow before measuring, you’ll add refrigerant to a misdiagnosed system and flood the coil later.</p> <p> A heat pump in cooling mode with a reversing valve that doesn’t fully shift can put part of the outdoor coil in the wrong configuration. The result is lukewarm air and strange temperature splits. The pressure readings look “off” in ways that don’t align with simple undercharge.</p> <p> A kinked liquid line hidden behind the siding throttles refrigerant flow, starving the evaporator. The system pressures might look similar to low charge, but the charge amount is fine. You find it by temperature profiling along the line set and feeling for sudden drops.</p> <p> A dual-capacitor that is marginal can pass a quick static test but fail when hot, letting the condenser fan slow subtly. Head pressure creeps up, the system unloads, and the supply air warms. The refrigerant charge gets blamed, but the fan speed was the true cause.</p> <h2> When replacement is smarter than repeated repairs</h2> <p> If the evaporator coil is riddled with pinholes and the outdoor unit is 12 to 15 years old, repairing the leak and recharging can cost half of what a new system costs. In many markets, a coil replacement plus refrigerant and labor runs $1,200 to $2,000 or more. Add a condenser fan motor here, a capacitor there, and you wind up spending close to a new, warrantied system that uses less energy and a refrigerant that will be easier to service long term.</p> <p> Age matters. So does compatibility. If your indoor coil and furnace are R-22 era and your outdoor unit is a mismatched R-410A condenser, you may already be compromising performance. The hvac system lifespan depends less on the calendar and more on maintenance quality, cleanliness, and proper charging. Still, once a system is over a decade old and springing leaks, I recommend a balanced assessment that includes replacement quotes. Cooling reliability in a heat wave often justifies the investment.</p> <h2> What a homeowner can check before calling again</h2> <p> Most homeowners can perform a few safe checks that provide useful information and, in some cases, resolve the issue outright. Keep it simple and safe: no opening sealed panels with line voltage, no messing with refrigerant.</p> <ul>  <li> <p> Ensure the thermostat is set to cool, the schedule is sensible, and the fan mode is automatic, not constant circulate if that creates warm-air complaints between cycles.</p></li> <li> <p> Replace or remove an overly restrictive filter. If in doubt, try a medium-efficiency pleated filter or a clean fiberglass filter briefly to test airflow.</p></li> <li> <p> Inspect the outdoor unit. Clear leaves and lint from the coil fins with a garden hose from inside out if you can access safely, or at least from the outside at low pressure. Ensure the top fan runs smoothly and at normal speed.</p><p> <iframe  src="https://www.google.com/maps/embed?pb=!1m18!1m12!1m3!1d3163.3723658700796!2d-84.5519346!3d37.930854800000006!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x88425991f2c8d667%3A0xd6a4fcd021fabe26!2sAirPro%20Heating%20%26%20Cooling!5e1!3m2!1sen!2sph!4v1767010042088!5m2!1sen!2sph" width="560" height="315" style="border: none;" allowfullscreen="" ></iframe></p></li> <li> <p> Check that supply vents and returns are open and not blocked by rugs or furniture. A closed return or choked supply in a central area can starve the system.</p></li> <li> <p> Watch for icing. If the suction line near the outdoor unit frosts up or there’s ice on the indoor coil housing, shut the system off and run the fan only to thaw. Report icing to the technician, since it helps them focus on airflow, charge, or metering issues.</p></li> </ul> <p> Those steps won’t fix a leak, but they rule out the obvious and help you communicate better with your service provider.</p> <h2> A note on heating complaints in the same system</h2> <p> Central air often shares a blower and cabinet with a gas furnace or electric air handler. If a homeowner mentions furnace not heating during winter and AC not cooling during summer, I suspect a core problem like poor airflow, incorrect blower settings, or control issues. One memorable case involved a blower motor wired for a low heat tap that could not deliver enough air for cooling. The heater not working complaint turned out to be a high limit tripping in winter and a frozen coil in summer, both due to insufficient airflow. The repair was a new ECM motor with proper programming, duct adjustments, and a coil cleaning. No refrigerant was needed at all.</p> <h2> What a thorough service visit looks like</h2> <p> If you’re scheduling a follow-up, you’ll want a technician who does more than connect gauges. Ask them to bring a micron gauge, an electronic leak detector, and a temperature probe set. Let them know you want numbers: static pressure, supply and return temperatures, target and actual superheat or subcooling, and the final measured charge by weight if refrigerant is recovered and re-added.</p> <p> A proper visit goes like this in practice: they evaluate filters and coils, measure static to confirm airflow, inspect electrical components, then run the system and gather baseline readings. If the readings point to low charge, they recover and weigh what comes out, pressure test, locate and repair leaks, replace the drier, evacuate deeply, weigh in the correct charge, and verify performance against manufacturer data. If the readings point to airflow or control issues, they address those first, then recheck refrigeration performance. That sequence prevents circular fixes and protects the compressor.</p> <h2> Costs and expectations</h2> <p> Diagnosing and fixing an AC that isn’t cooling after a recharge varies widely. A simple dirty coil cleaning might be a few hundred dollars. A serious leak hunt, coil replacement, and full refrigerant service can reach four figures. Adding a hard-start kit or replacing a failing run capacitor is modest, while replacing a condenser fan motor falls in the middle. Most homeowners spend less than a full system replacement to resolve a single well-defined cause. Repeated “add a pound” visits become expensive and damaging, especially now that many refrigerants have tightened supply and higher prices.</p> <p> Speed matters in a heat wave, but precision saves money. If your tech talks in specifics and shows measurements, you’re on the right track. If they won’t pressure test or evacuate with a micron gauge when a leak is suspected, consider another contractor.</p> <h2> Prevention that actually works</h2> <p> Proactive maintenance pays. Keep the outdoor coil clean, change filters on schedule, and inspect the evaporator coil annually in dusty homes. Ask for a quick static pressure check every couple of years. Make sure the condensate drain stays clear to avoid water backing into the coil pan and creating a biofilm that degrades coil surfaces. Check the thermostat calibration and location; a thermostat in direct sun or on an exterior wall gives bad guidance to an otherwise healthy system.</p> <a href="https://golf-wiki.win/index.php/Extending_Your_HVAC_System_Lifespan_with_Preventive_Maintenance"><strong>best hvac maintenance service</strong></a> <p> If you plan upgrades, address duct sealing and attic insulation. Lowering the building load gives the AC breathing room on extreme days, improves comfort, and extends the hvac system lifespan. Matching the blower settings to both heating and cooling demands avoids the whipsaw of a quiet but weak furnace paired with a suffocated AC.</p> <h2> The bottom line</h2> <p> If your AC is not cooling after a refrigerant recharge, the recharge likely missed the real problem. The underlying causes fall into a handful of buckets: leaks that were not repaired, airflow constraints that skew everything, contamination inside the system, metering device faults, or control and electrical issues. Occasionally, the house itself is the culprit. Solving it takes measured diagnostics, not guesses. Fix the root cause, and the system will reward you with steady, efficient cooling instead of another warm afternoon and another bill for more refrigerant.</p><p> </p><p>AirPro Heating & Cooling
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Address: 102 Park Central Ct, Nicholasville, KY 40356
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Phone: (859) 549-7341
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