As a homeowner, you probably are familiar with the overwhelming nature of maintaining your investment. From repairing a leaky faucet to installing new flooring, the challenges of home ownership are easy to see. Of course, certain updates are essential for the value and function of your house. Considering your heating and air conditioning system encompasses half of your home's total energy use, maintaining the system benefits the environment and your bank account. Using this guide on common noises in your outdoor units, you can diagnose and repair your heating system and air conditioning.


A periodic shaking or buzzing sound coming from your outdoor unit may be an electrical issue. Unfortunately, you probably do not have experience working around electrical wiring and parts, so contacting a heating and air contractor wise.

Your contractor will determine if there are any loose electrical connections in and around your outdoor unit. This may involve disconnecting power and inspecting the interior components to find the faulty connection.

If the shaking and buzzing sound occurs immediately after powering on your system, you may have tripped your breaker. However, if the noise continues, you may have a faulty relay switch.

Necessary for powering on your heating and air system, a faulty relay switch will not allow the system to heat or cool your home.  If the relay switch breaks, it creates a shaking, buzzing sound inside your unit. While important, replacing the relay switch is a simple, inexpensive task.


A loud rattling inside your outdoor unit is most likely due to a problem with your fan in the condenser. You may have a broken fan or a loose screw, but a detailed inspection is necessary to find the source of the rattling. Use the following steps to safely inspect the interior of your unit:

  1. Power Down Unit – Open the disconnect box, which is located near your unit. Turn off the power shutoff. Also, shut off the power to your unit at your indoor electrical panel.
  2. Remove the Grill – Use a screwdriver to remove the screws connecting the exterior grill cover. Pull the side grill cover up and lift off the top panel in one motion.
  3. Inspect the Fan – Inspect the fan blades inside your unit. If blades are loose, tighten the screws with your screwdriver. If blades are broken or warped, you will need to replace the entire fan.
  4. Inspect the Interior – If the fan and blades appear to be in good condition, check the interior for loose screws or bolts. Loose pieces create noise, but may not affect the working mechanism of your system. If left inside, they could lead to problems in the future.


When running your system, you will hear a soft humming noise. This natural sound stems from your system's motor and is a necessary part of heating and cooling your house. However, a loud humming is not only an annoying problem for your neighbors, but it can also lead to expensive repairs.

If your outdoor unit is humming loudly, you may have debris or foreign objects lodged inside. Grass clippings, leaves, mulch, trash, small birds, reptiles, or amphibians may get stuck inside the grill cover or in between the fan blades.

While the cost ranges from $100 to $250, a contractor can clean your units to ensure a clean, quiet, and energy efficient heating and cooling system. Not only will the contractor remove debris and foreign objects from your outdoor units, but they will also replace filters and inspect your entire system.

In most cases, removing debris and any foreign objects corrects the loud humming noise.

Maintaining your home's heating and air system can be challenging. However, with a bit of effort and professional help, you can diagnose and repair common problems in your units.