Mini Split Leaking Freon (6 Reasons Why And How To Fix)

This post may contain affiliate links, which means we may receive a commission if you click a link and purchase something that we have recommended.

Air conditioner refrigerant leaks aren’t uncommon. Unfortunately, it’s one of the most complex and expensive AC problems. In extreme cases, you may need to replace the air conditioner altogether.

So, what causes Freon leaks, and what can you do if you discover a leak? We answer these and several other refrigerant leak questions below.

6 Reasons why a Mini Split May Leak Freon

The most common cause of refrigerant leaks is the metallic line set’s erosion due to formic acid or formaldehyde corrosion. However, leaks can also occur for various reasons, ranging from improper flare connections to poor-quality line sets.

In the US, HVAC experts have identified the following as the most common causes of air conditioner refrigerant leaks;

1. A leaking Shrader valve

The Shrader valve looks like the tiny valves found in your car tire. Their primary purpose is to hold the refrigerant in place. They are also designed to allow HVAC technicians to access and test pressure or recharge the system without letting out the refrigerant.

Unfortunately, the Shrader valve can deteriorate with time. The rubber seals, in particular, can erode over time, creating small gaps at the seal. Since refrigerant is contained under pressure, any small gaps can result in a leak.

2. Poor flare connections

Flare connections are leak-proof connections that use flare nuts (slightly different from standard nuts) to connect the line set to the indoor head and outdoor condensing units. Standard air conditioners have four flare connections, while multi-zone systems can have more flare connections for the additional indoor air handlers.

Leaks can occur if the flare connection isn’t tight enough, if you over-tighten it, or if the flare is too tiny for the connection. Scarring in the flares and failure to oil the flare surface can also cause a refrigerant leak.

3. A leaky capillary tube

Capillary tubes are tiny copper tubes found in the evaporator coils. They can also be found in the condenser unit if your mini-split doubles as a heat pump. The tubes often vibrate when the AC is operating.

This vibration can cause them to rub against each other or other parts of the air conditioner, eventually creating holes in the tubes. Freon can leak from these holes.

4. Heat pump accumulator leaks

If your mini split AC doubles as a heat pump, you should know that it has what’s known as an accumulator. Heat pump accumulators allow the unit to provide heat in the cold season without exposing the compressor to slugging.

However, accumulators are made from steel. After a few years, the material may begin to eat away and rust. The deterioration can create gaps through which Freon may leak.

5. Leaking at the evaporator or condenser coils

The condenser unit outside the house and evaporator unit inside the house contain copper coils that air the heat exchange between the refrigerant and air passing through the air conditioner. These coils are typically held together with a tube sheet made of sheet metal.

Over time, and thanks to vibration, the parts where the coils bend can rub against the tube sheet, causing holes in the coils. Refrigerant can also escape via these holes.

6. Line set damage

Finally, line set damage is another common cause of Freon leaks. The line set is the set of copper tubes connecting the condenser unit outside the house to the air handler inside the house. These copper lines transport refrigerant between the outdoor and indoor unit and are critical to the cooling or heating process.

Unfortunately, the line set can be damaged too. Perhaps you had renovation work done around the line set, and the guys tampered with the tubes. Or maybe you hit the tubes with a lawnmower or weed eater. A pierced line set will undoubtedly result in a Freon leak.

Signs Your Mini Split is Leaking Freon

The worst thing about refrigerant leaks is that they are tough to diagnose. Sometimes it takes days to realize that you have a Freon leak. Locating the location of the leak can be even more challenging. Aside from a higher power bill, look out for the following symptoms;

Loss of cooling power

Refrigerant plays a central role in cooling (and heating). During cooling, it’s the refrigerant that transports heat from your home to the condenser unit outside, where the heat is released to the atmosphere. Therefore, you’ll notice a significant drop in cooling performance if there’s a Freon leak. In many cases, you’ll need to adjust the thermostat setting in an attempt to boost cooling output.

Registers not blowing cold air

You may also have a refrigerant leak if you notice that the registers aren’t blowing cold air. Of course, this doesn’t mean that you should automatically assume you have a Freon leak any time the registers aren’t blowing cold air. Perhaps the AC is set to “Fan Only” mode. However, if you’ve ruled out other possibilities, then it’s most likely a refrigerant leak.

Frozen evaporator coils

The air conditioner is self-sustaining in that it relies on the heat extracted from inside or outside the house to keep the coils from freezing. However, there won’t be enough heat to keep the coils from freezing when there’s a leak that causes insufficient refrigerant flow through the system. The result is usually frozen evaporator coils. The freezing may or may not cause dripping water on the floor.

A hissing or gurgling sound

Since refrigerant is kept under pressure inside the air conditioner, a leak often causes a hissing sound. The sound is especially clear when the AC is off. If it’s a large leak, it may instead produce a gurgling sound, similar to water flowing from a pipe with air bubbles.

Why You Should Be Concerned

Freon leaks are bad for the cooling process, your health, and the environment. The following are a few common risks associated with a refrigerant leak;

  • Reduced cooling efficiency: As we’ve already mentioned, a Freon leak can cause a loss of cooling power. The result is usually inefficient cooling and higher power bills. 
  • Discomfort: Leaking Freon often means that you can’t achieve your heating and cooling goals efficiently. Initially, you may attempt to remedy the situation by lowering or raising the thermostat setting depending on the season. However, after some time, even the higher/lower settings become unhelpful. 
  • It’s terrible for the environment: After extensive testing in the 1970s, EPA found that EPA is bad for the environment as it damages the ozone layer. It does so by trapping heat normally radiated from the earth out into space. 
  • It’s dangerous for your health: Refrigerant poisoning is a severe condition that can cause difficulty breathing, headaches, nausea, and vomiting. Overexposure can also cause skin and eye irritation and coughing. If left untreated, the poisoning can cause a buildup of fluids in the lungs, loss of consciousness, and fainting. 

How to Detect a Refrigerant Leak in your Ductless Mini Split AC

The signs and symptoms discussed above aren’t always a sure sign of a Freon leak. The following tests are needed to confirm beyond doubt that it’s a refrigerant leak;

Dye detection

The most common way to verify that you have a Freon leak is to perform a dye test. This process involves sending fluorescent into the HVAC system. After circulating inside the AC for a while, the dye will eventually put out if there are any leaks in the AC system.

Electronic detection

Special electronic equipment can also help you confirm leaks in your AC and even spot the location of the leaks. All you need to do is scan a cross-section of the refrigeration components outside the house. When a leak is detected, the electronic equipment sounds an alarm. Unfortunately, this method is impractical for hidden parts of the AC, such as the refrigerant lines running through the wall.

Nitrogen detection

Nitrogen detection is the most popular among HVAC technicians. The only downside is that it’s also more costly than the other options. The process involves removing all the remaining Freon from your AC and replacing it with nitrogen- held under higher pressure than the refrigerant. If there’s a leak, you’ll hear audible noises.

What to Do About It

The best way to deal with Freon leaks is to prevent any leaks in the first place. This means ensuring regular maintenance. However, if the leak is already happening, you have only one option – to call an HVAC technician.

As we’ve mentioned, Freon is a poisonous gas that can cause respiratory issues and even result in fainting. Therefore, you must never handle it yourself – unless you’re licensed to do so. If you aren’t, turn off the AC and call your HVAC technician right away.

The technician will begin by verifying that it’s indeed a Freon leak before determining if the problem is fixable. If repair is possible, you may need to replace a few parts. Otherwise, you may need to replace the damaged component, i.e., compressor unit, refrigerant lines, or indoor air handler.

Key Takeaway

Mini-split Freon leaks aren’t unusual. Also, they can happen for many reasons, including corrosion and natural wear and tear. If you experience a leak, fix the problem urgently as Freon is a poisonous gas that causes unconsciousness and fainting. It’s also bad for the environment.  

Leave a Comment