Noises Your HVAC System Should NOT be Making

Some of the noises your HVAC system makes are normal. However, other sounds are cause for concern and require professional help. But how do you know whether or not you should be concerned with a particular sound? How do you know whether or not something is breaking or is in the process of breaking in your HVAC unit? How do you know whether you’re about to end up in a hotbox for the summer (or an icebox for the winter) if you don’t fix whatever is making that horrible sound? Here are the telltale signs that you need to be listening for that indicate something’s wrong with your HVAC unit.

Squealing/Screeching – A squeal when the unit first turns on is common. But if the squealing sounds are coming from the blower motor, it might be a sign of a faulty belt or motor bearing problems. Belts are typically not a costly repair and should be replaced before they break or else the blower will stop turning. Plenty of blower motor units have oil ports for adding lubricant while other units are sealed. Noisy motors will usually stop being noisy when a lubricant is added as necessary. If you decide to lubricate the motor rather than waiting for an HVAC technician to do it, be sure to use the right oil. Don’t use the typical household oil products such as WD-40 or any 3-in-1 oils, as they’re not heavy enough for your motor.

Rattling, Banging, Clanking, Thumping – If you hear any of these sounds, they typically are signs of an issue with the blower assembly or motor. Rattling typically signifies a part coming loose in the HVAC system. This problem should be fixed before a part breaks or disconnects entirely. Sometimes, the assembly motor mounts can become loose, the blower might not be aligned, and/or the motor bearings might be where the noise is coming from. You’ll want a qualified professional to inspect the motor assembly.

Rattling Specifically From Outside Compressor & Fan Unit – There shouldn’t be rattling when the compressor unit fan turns on. Rattling might indicate that there is loose hardware or a failing motor. How loud the rattling sounds can also indicate how serious the issue is.

If the sound resembles a scream, the compressor could be failing. Humming can be an indicator of a failing capacitor or a faulty motor. Squealing noises alongside the rattling are also a sign of a capacitor or compressor that’s starting to fail.

Repetitive Clicking Sounds – It’s common for a clicking noise to happen when turning an HVAC unit on or off. That’s fine. It’s when you hear a repeated clicking noise that you need to pay attention. If you’re hearing it consistently from the control panel or outside compressor, there might be a faulty relay. There might also be an electrical control causing the relay to timeout and fail.

Hissing – If you hear hissing, it probably means that air is escaping from somewhere in your HVAC system. If the hissing seems to be coming from your walls, it’s probably an air duct leaking. In addition to being noisy, you’ll be paying for air you aren’t using because it’s leaking into your walls instead circulating throughout your home. Duct repair requires a professional fix, so when you hear loud hissing, call an HVAC technician.

But if the hissing isn’t loud, it’s probably not an air duct but an air vent. Usually, when you hear hissing, it’s the result of your filter not being set correctly. It could also be that you don’t have the right size filter, and that’s forming a gap in the seal. If that’s what’s happening, the air is pushing past or around the filter rather than being pulled through the filter. This can be fixed by making sure the filter is the correct size and that it’s appropriately placed so that there are no gaps.

Thwapping – Hearing a rapid “thwapping” sound while the blower is running means that something might be trapped in the blower blades. This is particularly likely for outdoor AC units, which are more likely to collect debris such as leaves, acorns, and more. Or there might be something inside the housing that’s touching the blower as it turns. It will sound the way playing cards do when attached to bike tire spokes. This doesn’t mean immediate trouble, but if it’s an object or debris causing this issue, you’ll want to have an HVAC professional look over your unit and system so they can find the problem quickly and remove the debris.

Any of these issues can be resolved by having an HVAC technician inspect your unit and system to figure out the issue. If you’re located in or around the Oklahoma City area, contact Comfort Xpress. We are a heating and cooling contractor that can send technicians to your home who will inspect your HVAC unit and system and repair it (or replace it) as necessary.