What is Causing That Sound From My HVAC Unit?

March 3, 2020

Modern HVAC units in Murrieta and Temecula are designed to operate relatively quietly, and they rarely exceed noise levels of 55 decibels or more. For context, that’s about as loud as a normal conversation. When different parts of an HVAC unit start to break down, however, they can make all kinds of strange noises. Different components will make different noises, and what you’re hearing can help give you an idea of what exactly is wrong with your HVAC unit. If the problem is severe enough, you may need to contact an HVAC maintenance service such as ProFlo to come out and resolve the issue.

Electrical Components

An HVAC unit uses multiple electrical wires, relays, and switches to control its various functions. These components often make clicking noises during start-up and shutdown, which is perfectly normal and nothing to be concerned about. However, if you are hearing a constant clicking throughout the HVAC unit’s operation, it can be a sign that your controls are defective or the thermostat is failing. Additionally, loose wiring can make a humming or buzzing noise. 

Fan Blades and Motor

A loose or unbalanced fan blade can start striking the side of the fan housing, causing a loud rattling or buzzing noise. A dying fan motor can also make a rattling or humming noise as it struggles to keep up with the rest of the system. 

The Compressor

If there are broken parts inside a compressor, or if the compressor has come loose from its mountings, it can make banging or clanking sounds. A damaged compressor or one with high internal pressure can start making a screaming noise; if you hear this, shut the AC unit off immediately and contact an air conditioning repair service provider. 


Fastener components like screws, nuts, and bolts are critical to any piece of machinery, HVAC units included. When fasteners start to break down, however, the components that they secure can begin to shake around in their mountings and create all sorts of chattering and rattling noises. Thankfully, most fasteners are very easy for an AC repair service to replace. 


It’s important that you keep the area around your HVAC unit clear of debris such as leaves, twigs, small rocks, and trash. If this debris gets into the AC system, it can cause chattering and rattling noises as it bounces around in a vent or air filter. If you hear a constant “thwapping” noise, there may be something stuck in the blower blades or their housing. 

Blower Components

The HVAC unit’s blower helps distribute air through a building. If a blower’s belts or bearings are failing or not properly lubricated, they can cause a squealing or screeching noise created from the friction between moving components. If a component inside the blower has come loose, it can also create rattling, thumping, and banging noises as it gets bounced around. 

No matter what part of your HVAC unit is making weird noises, you can trust the experts at ProFlo to fix the issue. We’re experts at air conditioning maintenance and repairs, and we’re a Carrier factory authorized dealer for HVAC systems. As a fully certified HVAC maintenance service provider, we have provided Murrieta, Temecula, and the rest of the Inland Empire with AC repairs for over twenty years. If you’d like to learn more about our AC repair services or schedule an appointment with one of our trained technicians, give us a call at (951) 694-1300.

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