If your AC is low on refrigerant again after a recharge, the system has a leak. Refrigerant circulates in a sealed loop of copper and aluminum and is never burned off or used up like fuel, so a system that needs more every season is losing it somewhere. Adding refrigerant treats the symptom for a few months and leaves the hole in place.
In Los Angeles this shows up in late spring, the first week the thermostat says 78 and the house says 85. The compressor has been running since April, the attic is past 120 degrees, and a small leak that was tolerable in March has become a warm-air problem. Below is what a leak looks like, how technicians find one, and when the repair stops making sense.
Why refrigerant does not get used up
Your air conditioner moves heat, it does not make cold. Refrigerant picks up heat at the indoor coil, carries it outside, and drops it at the outdoor coil, over and over, in a closed circuit. Nothing in that cycle consumes it. A properly charged system holds the same amount of refrigerant on its first day and its fifteenth year.
That is why the phrase "my AC needs a recharge every year" is the real diagnosis. The EPA tells homeowners to ask technicians to locate and repair leaks instead of "topping off" leaking systems, because topping off costs you repeat service calls and repair bills and makes the system perform worse in between. You can read that guidance on the EPA homeowners FAQ.
If you have been told your system "just needs freon," ask where it went. A good answer names a location. If this is the third time you have heard it, the math also favors a fix: two or three top-ups over a couple of seasons usually cost more than finding the leak once. Our breakdown of AC repair costs in Los Angeles shows where leak repairs sit against other common repairs.
Signs your AC has a refrigerant leak
Leaks rarely announce themselves. The symptoms build slowly, which is why many owners notice only in the middle of a heat wave.
Warm or lukewarm air from the vents while the outdoor unit runs. The air may feel slightly cool but never cold.
A system that runs for hours and never reaches the thermostat setting.
Ice on the copper line outside, or frost on the indoor coil. Low refrigerant pressure drops the coil temperature below freezing, and the ice then blocks airflow, which makes the cooling worse.
An energy bill that climbs with no change in how you live. A low charge makes the compressor run longer to do less work.
Two things in that list are worth acting on right away. Ice means you should switch the system to fan only so it can thaw, and not keep running the compressor. And a long stretch of low charge can overheat and damage the compressor, which turns a modest repair into the most expensive one on the system. Our guide to what Los Angeles heat does to an air conditioner explains why Valley summers punish a struggling compressor.
A recharge restores the pressure, the AC cools again, and the leak carries on. A pinhole that lost a few ounces over the winter loses them again, so a system that "needs a little freon every June" is telling you its leak rate. Each top-up costs money and puts more refrigerant into the air.
Why stop leak additives are a bad bet
You will find "AC stop leak" products online and at parts counters. They promise to seal a leak by circulating a sealant through the system. Most HVAC technicians avoid them, and the reasons are mechanical.
The sealant has no way to tell a leak from a metering device. It can harden inside the expansion valve or the narrow passages of a new coil, and then you have a clog on top of the leak.
It contaminates the system. Sealant can foul the recovery machine and gauges a technician uses later, and some technicians will decline to work on a system that has been treated.
It rarely works on the leaks that matter. A corroded coil, a cracked fitting, or a failed valve core leaks faster than any sealant can plug.
It can cause trouble with warranty coverage. Check your manufacturer terms before putting anything in the system.
A system also depends on an exact charge, and a can of sealant with a charging hose makes it easy to end up with the wrong amount. If a product promises to fix a leak without anyone finding it, treat that promise as a warning sign.
How technicians find a refrigerant leak
The goal is to locate the leak, so the repair can be quoted in writing before anyone starts.
Electronic leak detector
A handheld sensor sniffs for refrigerant along coils, joints, and line connections. It is fast and good at moderate leaks, but it can chirp at drafts and old residue, so the reading needs interpretation.
Bubble test
Soap solution goes on a suspected joint, valve, or fitting. A leak forms bubbles. It is a low tech, reliable way to confirm what the electronic sensor suggests, and it works well on outdoor connections.
Nitrogen pressure test
When the refrigerant is gone, the system can be pressurized with dry nitrogen, which is inert and safe, and watched. A drop in pressure confirms a leak, and the nitrogen drives out small leaks that bubbles and sensors can then locate. This is the standard way to prove a leak before a repair or after one, and it lets a technician test a repaired section without wasting more refrigerant.
UV dye
A small amount of fluorescent dye is added to the system, which runs for a while, and a UV light later shows the spot where it escaped. Dye suits slow leaks that are hard to catch in one visit. It is a diagnostic aid, and unrelated to sealant.
Ask which method your technician used and what they found. A real diagnosis names the part and the location, such as the Schrader valve on the service port or a pinhole on the evaporator coil.
Where leaks usually are: coil, line set, or valve
The location of the leak drives both the price and the decision.
Schrader valves and fittings
The small service valves on the outdoor unit have a tiny core, similar to a tire valve. Cores wear out, and a cap that was left off lets dirt in. This is among the cheapest leaks to fix, and a technician can often replace a core in minutes.
The line set
The copper lines run between the indoor and outdoor units, often through the attic or along an exterior wall. Vibration, rubbing against framing, and physical damage can crack a joint. Brazed joints can be re-brazed, and short sections replaced. A long run damaged by rodents or corrosion is a bigger job.
The evaporator coil
Indoor coils often leak from corrosion that eats microscopic pinholes into thin copper tubing. These leaks are hard to see and hard to patch, because the metal around a repair is just as thin as the metal that failed. The same is true of the outdoor condenser coil, which sits in sun and weather all day.
Coil leaks are the ones that decide whether a repair is worth doing, which is the next section.
Repair or replace when the coil leaks
A leak at a valve or a joint is a repair. A leaking evaporator coil is a closer call, and it comes down to age, refrigerant type, and warranty.
A newer system with a leaking coil is usually worth fixing. The part may still be under the manufacturer warranty, and a coil swap on a ten year old unit is a sensible use of money.
A system past roughly twelve to fifteen years with a coil leak is often at the point where the compressor and the rest of the equipment are close behind. Put new money into the oldest part of a worn system and the next failure usually follows.
If this is the second or third leak in a few seasons, the coil is likely failing across its surface, and patching one spot will not stop it.
If the system runs on R-22, the cost of refrigerant weighs heavily, as the next section explains.
Our guide on repair versus replacement gives the full set of tests, including the age-times-cost rule of thumb. We would rather tell you honestly that a repair makes sense than sell you a new system you do not need.
R-22, R-410A and the newer refrigerants
Refrigerant type changes the price of fixing a leak more than most owners expect.
R-22, also called HCFC-22, was the standard residential refrigerant for decades. Per the EPA, there has been no production or import of HCFC-22 since 2020, so a system that still uses it can only be serviced with reclaimed or previously produced supply. You can see the schedule on the EPA's HCFC phaseout page. The EPA also says there is no requirement to replace an existing R-22 system, so an older unit can legally keep running. A refrigerant leak on one, though, means paying for a scarce refrigerant again and again.
R-410A replaced R-22 in new homes and equipment. Now it is on its way out as well. Under the EPA's Technology Transitions program, starting January 1, 2025, new residential and light commercial AC and heat pump systems face a global warming potential limit of 700, which R-410A exceeds. The EPA notes there is no installation compliance date for systems where all specified components were manufactured or imported before January 1, 2025, so existing R-410A inventory is not stranded overnight. The details are in the EPA's HFC restrictions by sector table.
The newer refrigerants fall in a mildly flammable safety class, often written A2L. They are safe when handled properly, and they require technicians trained for them, and equipment designed for them. Practically, that means you cannot mix and match an old coil with a new outdoor unit, and a coil leak on a newer system can raise the question of replacing the matched indoor and outdoor set. Ask what your system uses. The data plate on the outdoor unit lists the refrigerant and the factory charge.
What to do when your AC is low on refrigerant again
Check the data plate and write down the model, serial number, and refrigerant type.
Ask for the leak to be found before any refrigerant is added, and ask which method was used.
Get the repair quote in writing, with the location of the leak and the price of fixing it versus replacing the part.
Ask how much refrigerant was added last time, and how much this time. Those figures tell you how fast the system is losing it.
Book a tune up before the heat starts. A maintenance visit that checks charge against superheat and subcooling, instead of adding by feel, catches slow leaks in spring. Our HVAC maintenance service covers this, and the AC repair service handles the repair itself.
A contractor who proposes a top-up with no plan to locate the leak is leaving the real problem for next summer.
Common questions
How often should an AC be recharged?
Ideally never. A sealed system keeps its refrigerant for its whole life, so a unit that needs a recharge every year or two has a leak. The right fix is to find the leak, repair it, and then charge the system to the manufacturer specification.
Can I just add Freon myself or buy a recharge kit?
No. The EPA says refrigerant for stationary AC equipment is only sold to certified technicians and the companies that employ them, and Section 608 certification is required to recharge it. Even where cans are sold online, guessing the charge can damage the compressor and does nothing for the leak.
Does AC stop leak actually work?
Rarely, and it carries real risk. Sealants can clog the metering device, contaminate the system, and complicate later repairs. They are not a substitute for locating the leak, and many technicians decline to service a system that has been treated with one.
Is a leaking evaporator coil worth repairing?
On a newer system, often yes, particularly when the coil is under warranty. On a system more than twelve to fifteen years old, or one with repeated leaks, the money usually goes further toward a replacement. A written estimate comparing both options makes the decision clear.
Get the leak found, not just topped off
If you are on your second or third recharge, stop adding refrigerant and get a technician to find out where it is going. A written estimate for the actual repair beats another seasonal top-up.
Our EPA certified technicians give you a written, upfront estimate before any work begins, with same-day service in most of Los Angeles. We serve Los Angeles, Calabasas, Sherman Oaks, Glendale, Pasadena and Burbank. Call (310) 469-1979 or book a diagnostic online.