Staying Up On Furnace Maintenance

Is Your Outside Air Conditioning Unit Making Strange Noises? When To Call In A Professional

The air compressor in your outside air conditioning unit is a heavy piece of machinery and will regularly make loud noises during normal operation. It's normal for the unit to make all sorts of banging and hissing noises, even when nothing is wrong with the unit. This can make it difficult, however, for homeowners to tell when a noise coming from the air conditioner unit warrants attention from a professional. Below are some noises that may come from your outside air conditioning unit and some advice on whether you need an air conditioning repair.

Loud Banging Or Rattling Sounds

These sounds usually indicate that something has come loose on the inside of the unit and is rapidly banging the sides of the unit during operation. Another explanation is that the fan in the outside unit is hitting something, which is most commonly caused by small tree branches that fall into the unit. In these cases, you'll need to stop operating your unit until you have a professional diagnose the problem, since running the air conditioner when it has a small object loose inside can cause further damage to the unit.

However, sometimes this isn't a problem that you need to worry about, especially in older air conditioner units. The springs in the outside air conditioner unit essentially act like your car's suspension by distributing the force from operating the compressor motor equally over the whole unit. If they break down, then you'll often hear loud banging noises that sound like a washing machine running. This makes an annoying racket, but it doesn't actually cause damage to the unit or suggest that the unit is ready to fail. If it's keeping you up at night, you'll want to contact a professional and discuss your options for sound dampening your air conditioner unit or replacing it with a newer, quieter model.

Constant Gurgling Or Hissing Noises

Sometimes a hissing noise coming from your outside air conditioner is normal. When your air conditioner switches from heating to cooling (or vice versa), it will engage its reversing pump and you will often hear a hissing noise coming from the unit during this time.

However, a constant hissing or gurgling noise likely indicates that you have a refrigerant leak within the outside unit itself. The pressure from your compressor could be causing small amounts of refrigerant to be forcibly pushed through a crack or gap in the unit, causing the hissing noise. You should check your refrigerant levels to see if you have a leak in the system; if the level of refrigerant goes down over time, the only possible cause is a leak somewhere in your air conditioning system since refrigerant is not consumed or used up during normal operation. You'll need to contact an air conditioner repair specialist to refill your refrigerant and find the source of the leak.

A High-Pitched Screaming Or Whistling Noise

This sounds similar to a tea kettle coming to a boil and is the worst sound you can ever hear coming from your air conditioner unit: it means that the compressor chamber is building up pressure but is unable to release it, usually because of a stuck valve. If you hear this sound coming from your air conditioner, you need to immediately cut the power to it from the breaker and keep your distance. It's rare, but there is a potential that your compressor may actually explode due to the buildup of pressure inside the compression chamber. Call a qualified air conditioner repair technician right away to inspect the unit before you attempt to operate it again.


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