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Why Is My Air Conditioner Making Noise?

Every time you turn on your air conditioner during the summer, you hear some normal sounds: The clicking noise as the machine turns on, or the flow of air as the blower sends it through the ductwork. On occasion, you may notice that there are sounds, loud or soft, that seem entirely abnormal. If you hear one of these noises coming from your HVAC system, you should schedule service.


The air conditioner motor and the blower fan rely on belts to function. Over time, these belts and bearings wear down and get too loose. As they start to wear out, they can slip out of place. The result is a screeching or squealing sound that you hear while the air conditioner is running. Even if the screeching stops after a few moments, you may need to have the belts fixed. In some cases, the bearings also need additional grease. Inspecting these parts is a common task in professional HVAC maintenance.


The blower fan sends cooled air to the ductwork. Your ductwork must be tightly sealed in order for the air to reach the right rooms, instead of just leaking out of holes and gaps in the ducts. Duct leaks can allow a significant amount of air to escape, making an obvious whistling sound. The cause might be as minor as loose registers or as complicated as poorly installed or damaged ductwork. Make a note about the location of the whistling, especially if it is happening in several places. This will help your HVAC technician know where to look for problems.


A piece of equipment that gets a lot of use for part of the year can certainly break down over time. In the exterior unit, sometimes debris or even animals get trapped inside. The equipment inside has a lot of moving components, and when some of these parts get loose, turning on the air conditioner can create a rattling sound as the piece hits the fan. In some cases, it is even the fan blades that have become loose or bent in some fashion. You want to have the problem repaired quickly, lest you find yourself having to replace the blower fan or other expensive HVAC components.


You will probably hear your air conditioner make a faint clicking sound as it turns on and off. In most cases, this is a sign of normal function as the power to the air conditioner is turned on. However, repeated or constant clicking could be a symptom of a faulty electrical connection, and you may need the services of an HVAC technician to identify and solve the problem.


Eventually, the motor for the air conditioner could wear out. As it does, it starts to make noises that get progressively louder and more disturbing. The sound may start out as a simple humming coming from your external air conditioning unit. A screaming noise indicates that the compressor is in serious trouble. Although a simple squealing sound at the beginning of the cycle may be normal, you do not want to wait to request service on the compressor. A broken compressor stops your air conditioner from working and is expensive to replace.


There are two types of liquids related to your air conditioner: refrigerant and condensation. Refrigerant runs from the air conditioning unit to the evaporator coil inside and back again. Condensation collects in the condensing unit and is drained outside through the condensate drain line. If either of the refrigerant or condensate drain lines are blocked or damaged in any way, you may notice a popping or gurgling coming from the exterior unit. It may even sound like running water. Low refrigerant charge is a likely cause. It must be dealt with as soon as possible, as it can damage the evaporator coil or other air conditioner components.

Scheduling Repairs

As a homeowner, you know it can be so irritating to have someone come out to inspect and fix a system only to have your system sound normal. The best thing you can do when you request repairs is to take notes about your observations. Sounds can be caused by a variety of possible problems, so you may not be sure precisely what has gone wrong. However, if you write down the time and frequency of the occurrences, as well as their location and anything that happened afterward, you may help narrow down the possibilities.
The sound of cool air coming through your vents may be music to your ears—until you hear a rattling or screeching noise. With these tips, you can have a better understanding of the source of the problem and how quickly you must have it repaired.

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