What to Do When Your HVAC Unit is Making Loud Noises

HVAC Troubleshooting: How to Fix Loud & Strange Noises Coming From Your AC Unit

A healthy, well maintained HVAC unit will typically run quietly, buzzing to itself in the background. Unusual or unexpected noises coming from your outdoor unit is a sign that your unit may be in some need of mechanical or electrical maintenance or repair. Some noises may signal dangerous situations which require immediate attention. Whether you prefer to do your own repairs or not, it is highly recommended that you have the contact information of local HVAC company with 24/7 availability.

There are a couple of warning noises you can be listening for. Be sure to address the issue as soon as you hear any of the following noises coming from your HVAC.

1. Squealing From the Blower Motor

This may be a sign of a bad belt or motor bearing. Replacing your belt is an inexpensive, fairly simple task. Make sure you get it done before it breaks entirely, as a broken belt will prevent the blower from turning. If your blower motor unit has oil ports for lubricant, this may also help soften the noises produced by the motor. The appropriate motor oil will vary from one HVAC unit to the next, so do your research ahead of time to make sure the lubricant you select is capable of completing the job.

2. Loud Rattling or Banging

A rattling usually means that either the fasteners on the metal cage which surrounds your condenser are not tight enough, or one of the components of your blower assembly or motor has come loose.

Fasteners can be fixed quickly by simply tightening the screws or bolts that secure the cage. If the problem lies with the blower assembly or the motor, you will have more complicated work to do. If this issue is left unaddressed, this rattling may progress into a louder banging. This indicates that whatever was loose has disconnected entirely.

Turn your HVAC off at this point. You may choose to do some investigative work yourself to determine what has become loose, or you may want to go ahead and call in a certified HVAC specialist. Common sources of this kind of noise include the motor bearings, the motor mounts or a blower which is out of alignment, but a professional can tell you for sure.

3. Clicking in Your Outdoor Unit

When your unit is being turned on and off, clicking noises are a normal part of functioning. However, a loud clicking noise, especially if it is coming from inside the cabinet, raises serious concerns. This is often an indicator that your capacitor is on its last legs.

Your capacitor works as a short term battery supply for your compressor as well as your blower motor and outside fan. Like any standard battery, these critical parts can wear down over time. A poorly functioning or failing capacitor can put an unsafe amount of stress on the compressor, causing to potentially overheat past the point of repair, which can put the health of your entire HVAC system in jeopardy. If you suspect your capacitor is the source of the clicking noise, immediately turn off your HVAC system. It is important to have a professional HVAC technician replace this part as soon as possible.

4. Humming From Your Outdoor Unit

Even with a completely dead capacitor, your compressor will still attempt to use it as a power source. This can burn out the entire compressor, leading to costly repairs. If your HVAC will not turn on and the clicking sound has turned into a hum, this very likely indicates that your capacitor is no longer providing power. In this case, turn your unit off immediately to prevent any further damage.

Often, these parts will fail during the most blistering parts of the summer. Warmer months means that your HVAC must work harder than ever, and this may put an increased amount of stress on already vulnerable parts. It is during these times when a well functioning air conditioning unit means the most to you that you may have to wait to longest for an HVAC specialist to become available, so it is important to act as soon as you sense a problem.

The good news is that a replacement capacitor is an inexpensive part and is fairly simple for the average homeowner to install. If you are confident in your handyperson capabilities, self-installation may save you a few hundred dollars in repair costs and save you days of wait time. However, incorrect installation can ultimately cost you more than simply having a professional do the job in the first place.

5. Loud Whistles or Screaming Noises

If your condenser unit is making a whistling or a screaming noise, you most likely have either a refrigerant leak, or there is something causing an excessive amount of internal pressure buildup. Both of these situations can be very dangerous, so your HVAC needs immediate attention. If necessary, you may need to contact an HVAC company with a 24-hour hotline. They will be able to advise you on the specific steps involved in what to do when your HVAC unit is making loud or strange noises, and may also be able to immediately dispatch a repair technician, depending on the severity of the situation.

6. Metal on Metal Sound

If a metal scraping noise is coming from the fan, the blades may be obstructed by a foreign object such as ice or loose wiring. Repeated contact with the foreign object while the fan is in motion can damage the blades as well as the motor of the fan. A bent or broken fan blade can crush the fins and tubing on the coil. Enough damage may also cause a refrigerant leak, which can cause a substantial decrease in overall heating and cooling efficiency. If you hear a metal on metal sound, stop your unit immediately to head off any potential damage.

Cleaning and clearing debris, as well as visually inspecting the fans for damage, should be a regular part of your HVAC maintenance routine, performed at least every other month.

Proactive Maintenance

If you are proactive about deciphering these signals and understanding what to do when your HVAC unit is making loud or strange noises before they grow into more serious problems, you will save hundreds of dollars in repair costs down the road. These are critical steps in extending the lifespan and efficiency of your air conditioning unit out to its maximum potential.