Tips & Resources
Smoothly operating furnaces and air conditioners are fairly quiet, and the noise they do emit is usually consistent and unobtrusive. Consequently, when you hear noises that are loud, grating or out of the ordinary, it could be a sign that something has gone wrong.
Here are six common sounds that could indicate trouble with your HVAC equipment…
A bad belt may be the culprit, and if it is that’s something you can replace yourself (and for a low cost). If fraying or stretching is evident replace the belt quickly, since it could break at any moment.
Another possible source of the noise could be a lack of lubricant, and your blower motor should have ports if you need to apply more oil. Make sure you purchase a motor oil that is appropriate for use with HVAC equipment, and if you aren’t sure what that might be ask your HVAC contractor for advice.
These sounds may indicate that something is coming loose in the blower assembly or motor. If so this is not something you can fix yourself, and even if you spot the unattached component you should still have a technician come and take a look.
Sometimes, rattling sounds can come from loose fasteners or screws somewhere in your HVAC system. You can check for this by inspecting and testing everything, and if you find anything loose you can tighten or re-fasten it yourself.
If these sounds originate from the outdoor compressor or indoor control panel, it could mean a relay is shot, or that an electric control is malfunctioning and causing the relay to work improperly. Either way, an HVAC technician can provide definitive answers.
If the clicking is confined to the outdoor unit of an air conditioner, it could be that the capacitor is about to fail. This could ultimately lead to compressor breakdown, and you need to summon a trained technician to inspect your HVAC system if you have reason to believe this could be the problem.
If an outdoor unit is emitting humming sounds, it means the capacitor has failed but the compressor is still trying to do its work. This will burn out the compressor in short order, and you must shut the unit down completely if a clicking sound has turned to humming.
Fortunately, the capacitor for the compressor is a relatively inexpensive part, and your HVAC contractor can send an expert out to perform the installation after selling you the new capacitor.
Whistling or screaming sounds emerging from a condenser (the outdoor section of your air conditioner) could be a sign of impending doom. It could mean that refrigerant is leaking, or that some other mechanical failure is causing a hazardous buildup of pressure inside the unit.
Needless to say, if you hear such noises you should shut the air conditioner off immediately, and contact your HVAC contractor right away since this could be a dangerous situation.
Metal-on-metal screeching sounds could indicate a bent, broken, or obstructed fan blade, if the noise is coming from the outdoor half of the air conditioner. After you’ve shut the HVAC system off, check the fan to see if there are obstructions, such as a branch or stick or other wind-blown item that may have fallen in through the fan’s grill, and if you find anything remove it.
Should metal-on-metal sounds come from a furnace or the indoor half of the air conditioner, it could mean that something is loose or broken, in which case you’ll need to summon a trained technician to handle the inspection and repairs.
In general, troubleshooting is perfectly fine if the source of the trouble is visible, simple to repair, and doesn’t involve any type of electrical or gas work. If you have any doubts, though, or lack the confidence necessary for troubleshooting, don’t be afraid to call your HVAC contractor to ask for professional assistance.
It never hurts to check things first on your own, but once you identify the reason for the unwanted noise you must take action quickly, before your furnace or air conditioner suffers permanent and irreplaceable damage.