It’s always nice to hear the air conditioner turn on with a soft, friendly whoosh.

It’s definitely not so nice to hear: bangs, hisses, pops, screeches, whines and buzzes.

These noises are trying to tell you that the AC system has a problem – usually a problem that requires an experienced technician.

Some home AC noises are like noises you hear when a car develops a glitch.

• Whining or squeaking sounds could indicate a frayed belt, just like the noises made by a car’s worn fan belt.

• And hissing in a car or home AC system may signal a leak in the refrigerant system. Remember that refrigerant is toxic; only a licensed technician should handle refrigerant problems.

• The hissing doesn’t always mean the refrigerant system is leaking. It could be a leak in the pump coil or valves, or holes in the capillary tube.

• Some home AC sounds go deeper than the AC system. Popping sounds indicate trouble in the ductwork that carries your cooled air into the rooms of your home. The ducts could have holes or leaks or be dislodged, meaning less cool air and higher utility bills for you.

• Does it sound like something is rattling around in your AC system?
Best case scenario: A few twigs got into the outside unit and can be removed easily.

Not so good scenarios: These are the death rattles of a deteriorating component or signs that a part needs tightening.

Bangs and buzzes: They are serious sounds. Your first act in either case should be to turn off the system. ASAP!

Banging noises often mean a key part has come loose and is probably inflicting damage on other components, which can entail costly repairs.

Buzzing can be an especially dire warning about loose wires or other electrical flaws – which can lead to a house fire. Call a HVAC technician for advice.

Some less scary causes of that buzzing noise: The condenser fan is stuck or the system may be frozen. If it’s frozen, keep the system off until everything thaws and then turn it on, but at a more mid-range temperature.

Screeches have a couple different meanings.

Non-stop screeching usually can be traced back to the fan motor. But if the screeching stops after a while, the problem could be in the compressor, usually an AC’s system’s most expensive part.

Again, turn off the system immediately and contact an experienced HVAC professional. We’re talking about costly parts; the sooner you intervene, the less damage will be done.

Other suspect sounds

While a strong AC system starts with a whooshing noise and other standard sounds, beware if you hear more clicks than normal. Those extra clicks indicate deterioration in the capacitor, which starts the AC motor.

High-pitched squeals are designed to get our attention, so ignore them at your peril. With an AC system, a squeal can mean an overly worn part, a beleaguered compressor, or something in between.

In any event, a savvy technician can trace the squealing noise to its source and solve the problem, and restore quiet and worry-free cool air to your home.

Premier HVAC services air conditioning, heating and ventilation needs in Brooklyn, Queens, Manhattan and Long Island.