Why is My HVAC Unit Making Weird Noises When It Starts?

Why is My HVAC Unit Making Weird Noises When It Starts?

Get answers from the pros to your HVAC general service questions.


We tend to take our HVAC for granted, until we have general service questions about why it might be making that hideous noise. Then we need help. And since most people are not HVAC technicians, it can be hard to find the information you need. Here are some tips for those who are experiencing that undetermined weird noise when their HVAC unit starts up.

Got Squeals, Screeches, or Squeaks?

There are belts inside your HVAC unit that work with the motor to run your system. That squealing you hear could be your belt going bad. Although this isn’t a crisis, you should have the belt changed before it breaks and shuts down your heating and cooling system.

Another cause of screeches and squeaks could be a motor bearing problem, which means it might be time to lubricate. Oil will keep the ports running smoothly and should eliminate the noise.

Rattle, Rattle, Thump

A rattling sound or thumping sound could mean something is coming loose in the motor or the assembly. If that part isn’t repaired, it could break off or break loose causing even more damage to the system. If it’s loud, turn off your HVAC system until you can have it repaired.

Rapping or Thwapping

At times something becomes stuck in the fan blades. This can cause a rapping, slapping, or thwapping sound. The item stuck needs to be removed to prevent an abnormal amount of wear on the motor caused by a slow-down in the fan mechanism from dragging the debris around and around.

There are many reasons your heating and cooling system could be making loud noises when it starts up. Instead of taking chances and trying to ignore it, call your HVAC dealer for a service call. It could save you money in the long run to catch it before it gets worse.

For quick response to your general service questions and for any necessary HVAC repairs, contact your local McCall’s Supply location.