Why is My Air Conditioning System Hissing?

If you hear a hissing from your air conditioning, you should have it repaired as soon as possible — for the sake of your comfort and the longevity of your system! Air conditioning system hissing is most commonly caused by leaking refrigerant, which has a big impact on your unit’s efficiency and effectiveness.

With humid weather sometimes lasting well into fall, this is a repair you should not put off. A closed system is essential to a properly functioning AC unit, meaning a leaky, low pressure system will function about as well as flat tires.

What is causing the hissing?

Leaky refrigerant lines

The copper refrigerant lines that make up an air conditioning system’s condenser are crucial for its cooling capabilities. A leak can develop anywhere along these cooling lines, but the worst location is by the compressor. Sometimes that leak might sound like bubbling instead of hissing, but in both cases your system is losing pressure. At a minimum, a repairman will need to locate the leak, empty the system, fix the leak and refill the refrigerant.

This repair should be performed by a professional as soon as possible. Otherwise, you risk damaging the compressor and possibly even replacing your system.

Summer air conditioning: Your guide to keeping cool

Internal valve leak

Your air conditioning system’s compressor has a valve that can leak and emit a hissing sound. This is also serious and needs to be fixed as soon as possible. Same as the leaky refrigerant lines, this problem decreases the pressure levels of your air conditioner. Low pressure will make your machine work harder using more energy and wear out sooner. Left unrepaired, a valve leak will get worse and louder.

The internal valve controls the pressurization of the refrigerant and is crucial to efficient air conditioning.

Compressor is malfunctioning

If you can trace the hissing back to the outdoor box housing air conditioner’s compressor, you have big problems. Hissing and shrieking is a certain sign that the pressure levels in your compressor are very wrong. If you hear shrieking, turn off your air conditioning IMMEDIATELY and do not restart it until an HVAC professional has taken a look.

The compressor is the most expensive part of an air conditioning system. For systems that are 8-15 years old, it’s often more economical to replace the whole system than get in there to make a repair.  

Read more: What’s wrong with my air conditioner?

Can I fix it myself?

While topping off your system with refrigerant fluid is certainly possible, there are several reasons why you should leave this task to the professionals.

It’s expensive!

Most air conditioning systems use a refrigerant fluid called R-22. The government is in the process of phasing out R-22 for the more efficient, environmentally-conscious R-410A, making R-22 expensive and inconvenient to buy.

It requires special disposal.

If you hire a professional to mend the leaks in your system, they’ll drain your unit of refrigerant before doing it, then fill it up with new fluid when the welding is finished. They take the old fluid with them for proper disposal, and you are saved several trips to pick up fluid and drop off waste for this chore.

Refrigerant can be harmful to your health.

Refrigerant is a tasteless and odorless gas, but has properties that suppress oxygen absorption in the lungs. Even minor spills can be mildly harmful, and consumers are advised by the CDC to avoid all exposure to this substance. A trained professional knows how to handle and dispose of refrigerant fluid safely, so leave the risk to them.

Learn more: What to know when you need a new HVAC system

Still not sure? Try this

Sometimes hissing is confused with the normal operational sounds of an air conditioning system. If you hear a small, short hissing sound, this is the normal sound of the expansion valve.

The ductwork at the beginning of a cycle can also emit hissing sounds. Try opening up the vents and registers more to try reducing hiss noises from ductwork. If this is the only place you hear hissing from, it’s probably not an issue.

Keep in mind that any long or constant hissing, crackling or popping noises should be evaluated by a professional.

Timely service makes a difference

To preserve the lifespan of your air conditioning system, call an HVAC professional right away to assess hissing sounds. By the time hissing is audible from your AC unit, it likely has a significant leak in the refrigerant line, or worse. A closed, pressurized system is essential to a properly working air conditioning system, and a low pressure system will be a huge drain on your electric bill.

If you need professional advice on repairing or replacing your air conditioning system, give John C. Flood a call. You can call us 24-hours-a-day, seven days a week to schedule an appointment. We look forward to ensuring your comfort for those muggy DMV summer days.

This Month's Special

$75.00 OFF

Any Plumbing Service

Minimum of $500.00 job to be applicable. Cannot be combined with any other offer or discounts. Limited time offer. Coupon must be presented at the time of the initial call. Discounts/promotions cannot be applied.

Expires: 04/30/2024

Share On Social


Follow Us

Sign Me Up for John C. Flood Savings and Updates:

Checkout Our Story

Need Service Now?