How to Tell If Your Air Conditioner Has a Gas Leak (And Where It Might Be Coming From)

If your air conditioner is running but not cooling properly, there’s a good chance you’re dealing with a refrigerant (gas) leak. This is one of the most common faults in both split system and ducted air conditioning systems.

The tricky part is that gas doesn’t just “run out” like fuel. If your system is low, it almost always means there is a leak somewhere that needs to be found and repaired.

Here’s how to recognise the signs of a gas leak—and where it’s most likely coming from.

One of the earliest and most obvious signs is poor cooling performance. The system may still blow air, but it feels:

• Lukewarm instead of cold
• Weak or inconsistent
• Ineffective even on full settings

Low refrigerant levels can cause the evaporator coil to drop below freezing, leading to:

• Ice on indoor coils
• Frozen pipes
• Ice buildup on the outdoor unit in some cases

If you see ice, turn the system off and allow it to defrost before further diagnosis.

A refrigerant leak sometimes produces a faint:

• Hissing sound (gas escaping under pressure)
• Bubbling sound (refrigerant moving through a leak point or oil/gas mix escaping)

These noises are often intermittent and easiest to hear when the system first starts or stops.

When refrigerant is low, the system works harder and runs longer cycles to try and reach temperature. This leads to:

• Increased power usage
• Longer running times
• Reduced efficiency overall

Refrigerant leaks are often accompanied by compressor oil escaping. You may notice:

• Dark or oily patches on copper pipe joints
• Dust sticking to oily areas near connections
• Slight discolouration around flare joints or valves

If your air conditioner is running but not cooling properly, there’s a good chance you’re dealing with a refrigerant (gas) leak. This is one of the most common faults in both split system and ducted air conditioning systems.

The tricky part is that gas doesn’t just “run out” like fuel. If your system is low, it almost always means there is a leak somewhere that needs to be found and repaired.

Here’s how to recognise the signs of a gas leak—and where it’s most likely coming from.

Flare connections between copper pipes are one of the most common leak points, especially if:

• The flare wasn’t tightened correctly
• The pipe has vibrated over time
• Poor installation practices were used

These leaks are often small but persistent.

The indoor coil can develop leaks due to:

• Corrosion over time
• Moisture exposure
• Manufacturing defects (rare but possible)

Coil leaks are more serious and can sometimes make repair uneconomical depending on access and cost.

The outdoor unit is exposed to weather, salt air, and debris. Leaks here are commonly caused by:

• Corrosion from coastal air
• Physical damage (impact or vibration)
• Long-term wear and tear

Small but important components, these valves can leak due to:

• Worn seals
• Loose caps
• Internal valve failure

These are usually repairable without major system work.

In ducted systems, leaks can sometimes occur at:

• Factory joints
• Installed pipework joints
• Areas exposed to vibration or movement

The advantage with ducted systems is that leaks can often be isolated and repaired without replacing the entire unit.