3 Factors That Can Cause Your HVAC Condensing Fan to Become Loud

The condensing unit fan plays a vital role in keeping your unit functional and preventing overheating that would shut down the cooling process. A major problem with the motor of blades would become immediately evident, since your unit would start closing down each time it overheated. But some more minor issues can lead to a noisy fan, which can eventually become more than just a sound problem.

What factors can cause your HVAC condensing fan to become loud? And how can an appliance repair or HVAC services company help?

Trapped Debris

The fan guard on top of the condensing unit and parts of the unit itself has a grate that allows for air to circulate throughout providing the needed overheating protection. Those grates can also allow dirt and debris to swirl around and potentially get stuck in the blades, and that would create noise each time the blades spun and ran into the debris.

You can check the fan pretty quickly for stuck debris. Start by checking the exterior grates for signs of trapped debris and removing any leaves or twigs you might find. You can then turn off the electricity to the unit at the circuit breaker merely as a precaution.

Use a socket or screwdriver to loosen and then remove the fasteners holding the fan guard onto the condensing unit. Lift up on the fan guard carefully, since the attached fan assembly is a bit hefty. Flip the guard over and rest the guard on the unit's top, and you should now have the fan blades facing you for easy inspection.

Check for any signs of dirt or debris stuck in or around the blades. Remove what debris you can manually, and then follow up with a steel brush, if needed.

Loose Fan Blades

Did the fan look clear of debris during your inspection? While you have the fan out, test to see whether the blades have become loose as they spin around the motor shaft. Twist the blades with your hand and make sure the blades move smoothly with no wobbling. If you feel wobbling, you need to tighten the set screw on the side of the fan blades.

Tighten the set screw using an adjustable wrench. Conduct another test spin to make sure the wobbling has stopped before putting the unit back together.

If the fan blades were clean and free of wobbles, but you did feel some resistance, you might have a bigger problem in your hands.

Dying Fan Motor 

The resistance indicates the shaft itself is experiencing problems, and that shows a motor issue. You will want to leave motor testing up to a professional HVAC services tech because, if broken, the part will need immediate replacement so that your unit doesn't end up with an entirely nonfunctional fan that would trigger constant overheating.