5 Signs Your Aircon Refrigerant Is Leaking

A refrigerant leak does not usually happen all at once. Most leaks start at joints, flare connections, or corroded spots on the copper piping. The gas escapes slowly — often over weeks or months — so the cooling drops gradually. The room feels a little warmer each week, but the change is small enough that most people adjust their habits before they notice the unit is underperforming.

By the time the cooling failure becomes obvious, the system may have been running on low charge for a long time. Running on low refrigerant forces the compressor to work harder and hotter, which accelerates wear on the most expensive component in the system. Recognising the early signs gives you a chance to fix the leak before it causes secondary damage.

When refrigerant level drops, the pressure inside the evaporator coil falls below normal. Lower pressure means a lower boiling point, which causes the coil surface to drop below freezing. Moisture in the air condenses on the coil and freezes. You may see frost or ice on the insulated copper pipe where it connects to the indoor unit.

Ice on the pipe is one of the most visible signs and often the first one homeowners notice. It can also be caused by a blocked filter or a faulty expansion valve, but combined with any of the other signs on this list, it strongly suggests a refrigerant shortfall. If you see ice, turn the unit off to let it thaw before running it again — operating with a frozen coil can damage the compressor.

A healthy system maintains consistent cooling month after month. If the room used to reach the set temperature comfortably and now takes longer — or never quite gets there — something has changed. A slow refrigerant leak produces exactly this pattern: steady, gradual decline in cooling performance.

This sign is different from a sudden cooling loss, which usually points to a mechanical fault like a failed compressor or a tripped breaker. The gradual nature of a leak makes it easy to blame on weather or imagination. If you find yourself lowering the thermostat to get the same comfort level you had before, the system may be losing charge.

Refrigerant under pressure escaping through a small opening produces a faint hissing or bubbling sound. This is most audible near the flare connections where the copper pipes join the indoor or outdoor unit. The sound is subtle and usually only noticeable when the room is quiet and you are close to the unit.

Not every hiss means a leak — normal refrigerant flow through the expansion valve can produce a soft sound too. But a hiss that is louder than usual or that was not there before is worth investigating. A technician can apply soap solution or use an electronic leak detector at the joints to confirm whether gas is escaping.

Refrigerant carries a small amount of compressor oil as it circulates. When gas escapes at a joint, it brings traces of this oil with it. The gas evaporates into the air, but the oil stays behind as a greasy film on the surface near the leak point. Oily patches on copper fittings, flare nuts, or the pipe insulation near a joint are a strong indicator.

This sign is easy to spot during a visual inspection if you know where to look. Check the flare connections at both the indoor and outdoor unit, and any joints along the pipe run. Fresh oil residue means the leak is active. Dried, darkened residue may indicate a slower or older leak. Either way, the joint needs attention.

As the refrigerant charge drops, the system loses its ability to transfer heat effectively. The compressor still runs, the fan still blows, and cold air still comes out of the vents — but the air is not as cold as it should be. The thermostat keeps calling for cooling, the compressor keeps running, and the room stays warmer than the setpoint.

This symptom overlaps with compressor weakness and undersizing, so it needs to be combined with other signs to point to a leak specifically. If the unit used to cool the room fine and now it does not, and you also see ice or hear a hiss, the combination narrows it down. A pressure reading confirms it — suction and discharge pressures below the normal range for the ambient temperature indicate low charge.

Do not request a gas top-up as the first step. Topping up without fixing the leak means the gas will escape again, and you pay twice. The right sequence is: confirm the leak with a pressure test, locate the leak point using detection methods, repair the joint or section of pipe, vacuum the system to remove moisture, and then recharge with the correct amount of refrigerant.

If the leak is at a flare connection, the repair is usually a matter of remaking the joint. If the leak is in a corroded section of pipe or inside the coil itself, the repair is more involved and may require replacing the affected component. A technician who has located the leak can explain the options and costs before any work begins.