Air conditioners make many different sounds, even when they’re brand new. When the air conditioner in your Randallstown, MD home starts up, you’ll likely hear the gentle rumble of its motor and the steady hum of air moving through your ductwork. When air conditioners are marketed as offering quiet operation, this doesn’t mean that they are absolutely silent while getting their jobs done. However, if your air conditioner starts making hissing sounds, the culprit could be the compressor. Here are several common causes of hissing at the AC compressor and a few tips for resolving this annoying problem.

Where Is the Hissing Sound Coming From?

Your air conditioner has an outside condenser and an indoor air handler. The air handler contains the unit’s evaporator coils, which is where heat is absorbed from warm air before distributing cool air through your home. The outside condenser houses the unit’s compressor. The compressor pumps pressurized refrigerant throughout the cooling system.

If your air conditioner is making hissing noises, they are likely coming from outside your home. Given the compressor’s outdoor location, your first thought may be that the condenser is harboring a frightened animal or an angry snake. However, hissing noises at the compressor unit are usually cyclic and easily distinguished from animal sounds. More often than not, they start at the beginning of each cooling cycle and last just 10 to 15 seconds. If your air conditioner is short cycling, step outside and listen for signs of trouble.

AC Hissing and Refrigerant Leaks

Refrigerant is the lifeblood of your air conditioner. This fluid absorbs the heat from your indoor air and releases it outside. Air conditioning systems and the refrigerant they contain are highly pressurized. This pressure allows for heat transfer, moisture removal, and reliable functioning. When refrigerant leaks out of air conditioning systems or when too much refrigerant is added, the pressure levels fall below or exceed the level needed for safe AC operation.

Some air conditioners can continue functioning for a long time despite having refrigerant leaks. Thus, even before you hear hissing noises at the outdoor unit, there may be other indications of leaking. These include:

  • Increasingly high home cooling costs
  • Longer cooling cycles with less indoor comfort
  • Freezing at the evaporator coils
  • Warm air coming from your HVAC air vents

Most air conditioners last between 10 and 15 years. If your air conditioner is nearing the end of its lifespan, you can expect a near-constant stream of wear-related issues. Refrigerant leaks are a common age-related problem. They occur when the rubber seals on service valves wear thin, shift out of place, or fail. In addition, metal within air conditioners is constantly exposed to temperature and chemical changes, causing it to erode gradually. In air conditioners that use older refrigerants, the harsh chemicals further contribute to the breakdown of components that keep refrigerant from seeping out.

Scheduling routine air conditioner maintenance minimizes the risk of refrigerant leaks by allowing HVAC technicians to identify worn seals, valves, and tubing before it becomes a significant issue. During a maintenance visit, these parts are replaced as needed so that air conditioners can continue functioning without interruption. HVAC technicians also look for signs like “champagne bubbles” on evaporator coils. These small drops of refrigerant coat evaporator coils and eventually lead to icing.

Unfortunately, even diligent AC maintenance cannot prevent the inevitable. Swapping out worn components will only solve the problem until the next worn component fails. If you have an age-related refrigerant leak causing your AC compressor to hiss, the most cost-effective solution is to replace your AC unit.

If your air conditioner is relatively new, leaking refrigerant could occur due to faulty installation or defective equipment. The ongoing refrigerant loss places AC compressors under tremendous stress. Continuing to use your air conditioner despite hissing sounds and other indications of a leak could result in premature compressor failure.

AC Compressor Pressure Changes = AC Hissing Sounds

If refrigerant is the lifeblood of your air conditioner, the compressor is its heart. Your AC needs the right amount of pressure to function normally. Insufficient pressure due to refrigerant loss can cause the compressor to collapse, and excess pressure can lead to disaster. Fortunately, newer AC models have built-in measures that turn air conditioners off when compressor pressure rises too high.

Among the most likely causes of excess pressure are pinched components inhibiting refrigerant movement and having too much refrigerant. If your air conditioner has excess pressure, you might hear a short hissing sound when it is on, but your cooling system will refuse to stay on. Air conditioners with compressor issues can turn themselves off and stay off, or they may eventually cycle back into action. Short cycling paired with hissing noises can indicate either insufficient or excess pressure. Only a licensed HVAC technician can accurately determine what is happening within your unit.

Hissing Sounds Don’t Always Come From the Compressor

There’s also the possibility that your AC compressor isn’t responsible for the hissing noises you hear. For some AC models, short hissing noises are fairly normal. With these units, hissing occurs every time their thermostatic expansion valves open to relieve pressure. However, thermostatic expansion valves are indoor components. The hissing noises they make always originate inside the home. This might be the source of your air conditioner’s hissing if you aren’t noticing other problems during operation and cannot hear hissing outside. Whenever hissing is paired with short-cycling, inefficient cooling, or increasingly high home energy bills, AC compressor problems are likely at play.

Reasons to Avoid Do-It-Yourself Repairs at the AC Compressor

With newer air conditioners, compressor issues are often service-related or a result of defective components. Your air conditioner may have arrived with a broken valve or hose, or your AC technician may have overfilled your refrigerant. In both cases, the necessary solution should be covered by either your manufacturer’s warranty or the labor guarantee provided by the responsible HVAC company. Taking matters into your own hands could void both of these protections and leave you paying for repairs or a compressor replacement entirely out of your own pocket.

There are also many dangers associated with do-it-yourself compressor repairs. The refrigerant moving through this component is often hot and under extreme pressure. AC refrigerants contain chemicals that are highly hazardous to human health when mishandled. Finally, the AC compressor is easily the most costly component in your cooling system. Failed DIY repairs can cause damages that result in the need for an immediate air conditioner replacement. It is almost always cheaper and safer to have a professional diagnose and resolve compressor problems instead.

At HB Home Service Team, we proudly serve Randallstown, Maryland and the surrounding communities. We offer heating, cooling, plumbing, and well services. We also provide carbon monoxide detection and HVAC preventative maintenance plans. If your AC compressor is making hissing sounds, we’ll find out why and solve the underlying problem. Contact HB Home Service Team now to schedule an appointment!

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