Weird Noises Coming From Your Air Conditioner?

It can be hard to tell when your air conditioner isn’t running quite right, but judging how it was when it was new, you might be able to hear when something’s off. If you notice strange sounds coming from your air conditioner, it’s likely due for repair.

Limcan Certified technicians have 60 years of experience diagnosing HVAC problems, so we can share a bit about what certain noises might mean.

Why Your Air Conditioner Might Struggle

Thanks to nearby Lake Ontario, Whitby and area’s annual humidity remains relatively high, at 66% based on averages collected from 1985-2015 just outside of Toronto.

The more humid the air is, the better it is at retaining heat. Water absorbs heat so effectively because of the particular way water molecules interact with each other, which causes them to absorb heat slowly and release energy just as slowly.

Managing Your Expectations

Since you first started using it, wear and tear causes your AC not to work as well as it used to. That means your air conditioner might naturally struggle the longer you have it. Most air conditioning systems last 8-15 years, so if your AC is older than that, it might be time to have a new AC installed.

The key to prolonging the life of your air conditioner is getting the right air conditioner maintenance. You should schedule air conditioner maintenance once per year to make sure your AC is working properly and efficiently.

Weird Noises Your Air Conditioner Might Be Making

Old, rusty, noisy air conditioner mounted to a dirty wall

Generally, air conditioning falls into two categories: central and ductless air conditioning. The difference lies in whether the AC integrates with your HVAC system’s central ventilation ducting. Which system you have will affect what different noises could mean. 

What Noises from Your Central Air Conditioner Mean 

Loud Whirring

Air conditioners built in more recent years are supposed to be quiet. If you hear a loud whirring at the HVAC unit, it might mean the blower fan doesn’t work well anymore. 

Blower fans move a lot of air through ducting, so there could be something wrong there, and it might continue when the furnace takes over in the winter. The cause could be age, unusual dirt and grime buildup, or mechanical failure due to insufficient maintenance.

Grinding & Screeching

The air filter in the blower duct might need to be replaced. Dust and grime buildup on the filter can create a backflow of air, which can make slight grinding or screeching noises as the blower tries to push air that just isn’t coming through.


Refrigerant lines near the evaporator can sometimes develop leaks and that might make dripping sounds inside the main intake duct. It might be all good on the inside, but you should check for weird sounds coming from the main components in the compressor as well.


Refrigerant lines can develop leaks anywhere on the lines, and that might make dripping sounds inside the compressor unit, rather than the tapping sound from inside a metal duct. Anytime water collects where it’s not supposed to, there’s a risk of mold and mildew forming.


The compressor unit’s motor might worn out. An overworked compressor might buzz as it contends with low refrigerant levels. Another cause for an overworked compressor can be that the intake has been blocked by shrubs or bushes, meaning the fan for cooling the compressor’s motor isn’t doing its job.


A capacitor is an important part of the air conditioner’s assembly. It provides considerable startup electricity for the compressor to run. Capacitors wear out over time, meaning the compressor doesn’t have the startup electricity needed. 

If the capacitor is nearing the end of its life, it lugs, maybe making buzzing sounds as it struggles to generate the necessary voltage and current.

What Noises from Your Ductless Air Conditioner Mean 


Ductless AC tends to be a compact unit, so the compressor’s fan has a greater chance of whacking other parts of the unit when seals degrade or mechanical issues happen. Clunking isn’t limited to ductless air conditioners, though.

Because wall-mounted or spit systems contain the compressor and the blower fan in the same housing, you might have trouble locating different sounds. 

Split systems are easier to check than wall-mounted since there’s a barrier between the compressor’s side and the blower’s side.

Wall-mounted units have especially clustered components, but if you identify each part and listen closely, you might be able to isolate and categorize the sounds.

Leave Air Conditioner Repair & Maintenance to Professionals

If you counted 1 or more of these noises, your air conditioner might be in need of repair or replacement. The friendly technicians at Limcan Heating and Air Conditioning are happy to take a look, whatever the case. And if it is time to replace your AC, we offer free in-home assessments.