1,963 posts, read 3,537,811 times 13,664 posts, read 13,229,960 times Originally Posted by cl723those are the best kind of service calls for both you and the service tech. Could you describe the noise as if air escaping from a balloon that gets progressively quieter? I presume it eventually stops after a minute or two. 1 posts, read 9,747 times 1 posts, read 9,656 timesSo your A/C is working fine but makes a loud slamming-like noise when it shuts off. What could be causing it? There are a number of possible causes. We’ve broken down the most common by where the noise is originating from: inside or outside of your home. Keep in mind, though, that without hearing the banging sound ourselves, it’s difficult to correctly diagnose. So for added peace of mind, we always recommend having a professional A/C tech take a look (especially if this is a new noise). Complaint: It sounds like there is a door inside the ducts that is slamming shut when the air conditioner turns off.

Most homes in the Phoenix area have return vents located in the ceiling of the home. A typical return vent in the ceiling of a Gilbert home. And inside the grilles of these vents is your air filter. The same return vent open, showing the filter and duct behind the vent. When your air conditioner turns on, these ducts suck in air from your home. Under certain conditions, the air filter may get sucked up against the top of the duct box. Then, when the A/C turns off, the filter drops to the grille, making a slamming or thumping noise. This is not a normal operating noise and is usually a sign of one of the following underlying problems: Some homeowners install highly efficient air filters to improve the air quality of their home. Normally, this is a good idea. But if you get a filter that is too efficient (noted by a MERV rating of 10+) and only 1-inch thick, it can restrict the amount of airflow through the filter. As the air conditioner tries to pull more air through the filter, the filter itself can get sucked up into your ductwork.

The fix: You have 2 options: When your air filter gets too dirty, the dirt restricts the airflow to your air conditioner. And just like we explained above, that can cause the filter to get sucked up into the duct as the A/C attempts to pull in more air. Related: How Your Dirty Air Filter Can Betray You The fix: Clean or replace the air filter. If your return ducts are too small, the speed of the air going through the returns can get powerful enough to suck an air filter up to the duct. The fix: You’ll need an A/C repair company to run new ductwork. Some air conditioning systems have dampers in them to change the amount of airflow flowing to different parts of your home. The slamming noise may be the damper closing after the A/C shuts off. The fix: You may not need to do anything, as this could be normal operation. But if the banging is extremely loud, contact an HVAC company to check it out, as the damper may need to be repaired or replaced. If you have sheet metal ducts, you may be hearing creaking noises from the ducts expanding and contracting from the pressure and temperature changes.

The fix: Most likely your ducts are improperly sized for the amount of air going through them, which is what’s causing them to “pop” as your air conditioner turns on and off. car ac repair albany gaOr the ducts might not be reinforced properly. 4 ton ac unit goodmanYou’ll need to have an A/C company find and fix the duct problem.portable ac unit sam's club There may be a problem with the fan in your indoor unit (or air handler) that’s causing the blower wheel to bang against another part of the unit. For example, the fan’s mounts can get loose, which can throw it off balance as it slows down, causing it to hit its enclosure. The fix: The blower wheel assembly may need to be repaired or replaced by an A/C professional. Complaint: When your A/C condenser (outside unit) shuts off, there’s a loud bang that sounds like something hit a wall.

The compressor is the part of your outdoor unit that pumps refrigerant to and from your indoor unit. Parts of an A/C system showing the compressor. Image source: Don Vandervort, HomeTips And inside the sealed compressor casing are many parts, including the refrigerant pump. Most of these pumps are mounted on support springs. But when a support spring breaks, the pump isn’t held evenly any longer. This makes it sort of like a spinning top: when it’s going quickly, its momentum keeps it upright and balanced. But as it slows down it starts wobbling. It’s the same for a compressor with a broken spring. When the air conditioner turns off, the pump loses momentum, which can cause it to knock against the case of the compressor and create a banging or slamming noise. The fix: To get rid of the noise, you’d have to replace the whole compressor since it is a single, sealed part. And replacing a compressor is expensive! So, if it’s not under warranty, we recommend you just leave it.

The sound isn’t necessarily an indication that the compressor will fail anytime soon. Your outdoor unit also contains a fan. And just like the indoor fan, parts can become loose. And then the fan can hit other parts of the outdoor unit, causing a slamming sound. The fix: Depending on the issue, you may need a whole new fan assembly, or a few bolts may need to be tightened. To figure out which of these problems is causing the slamming noise you’re hearing, you need a trained tech to listen to it. If you’re in the Phoenix area, George Brazil can help. We’ve been serving the Valley since 1955. Identifying Air Conditioner Noises and Smells Sometimes unpleasant smells and noises coming from an HVAC unit can indicate a problem with the system that could require maintenance orIf you’re experiencing air conditioner noise or if your air conditioner smells a bit funny, there may an issue inside your system. Components that could experience these problems include:

• Compressor – While compressors are noisy by nature, if your compressor is making loud or unusual noises, it may be worn out. • Drive Shaft or Fan Blower Motor – If the drive motor is making loud noises, it may need some lubrication. All motors need to be lubricated at all time, otherwise it will wear out. Loud noises may be either• Fan Blade – If one of the fan blades break off, it can start rubbing against the house and cause unwanted noise. If the air from your system smells musty, it may be due to mold and/or mildew buildup in your duct system. One way to get rid of this is to change the filter and clean the drip pan in your HVAC system. Clean using bleach or white vinegar to make sure the area is no longer hospitable to mold growth. Common furnace noises and their causes There are several furnace noises listed below, some of which could indicate a problem with the unit. If you’re concerned about a furnace

noise contact your local American Standard dealer to schedule an HVAC check-up: • Screech – This could be a problem with your motor or fan• Chirp – Chirping sounds are fairly common with furnaces and usually the natural noise of the mechanisms. Rattling noises typically happen when the system is cooling down and it not usually cause for alarm. • Boom – When the weather outside warms up or cools down, the ductwork in your house expands andIf this happens and your furnace smells like it’s burning, you might have a dirty burner in your furnace or a defective gas• Ping – This sound can also be caused by contracting • Hum – When the furnace burner lights, it may cause a humming• Whine – Whining or odd vibrating noise may indicate a problem with your furnace. • Crackle – Crackling noises may be the metal parts cooling down after the furnace shuts off. Clunk – Clunking or bumping sounds often means you have a cracked belt.