AC making loud noise again after repair
The air conditioning unit is repeating a loud noise even after a recent repair, requiring the entire system to be switched off to stop it. This ongoing malfunction prevents the unit from operating normally and leaves the home without reliable cooling.
What the numbers show
Counted from the threads quoted below. How we count
- People have been saying this in most months since September 2026.
- This comes up 23.1× more often in r/hvacadvice than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Replacing the air filter2 people mentionedDid this help you?
- 2Fully turn off the AC switch to stop the noiseDid this help you?
- 3Turning off the thermostatDid this help you?
- 4Spraying debris off the unitDid this help you?
- 5Digging old oscillating fans out of the garageDid this help you?
- 6Ensure the unit has a slight fall to the outsideDid this help you?
- 7Make sure any drain ports are clearDid this help you?
- 8Accepting the technician's assurance that the noise is normalDid this help you?
- 9Listening for refrigerant sloshing to check if the unit is runningDid this help you?
- 10Waiting for the installer to return and inspect the systemDid this help you?
- 11Turn off the air conditioner unitDid this help you?
- 12Go find a replacement at Home DepotDid this help you?
- 13Checking or questioning the stability of the mounting bracketDid this help you?
- 14Waiting to see if it stops on its ownDid this help you?
- 15Checking if a clog self-clearedDid this help you?
- 16Cleaning tubing and pipes from the air break back to the panDid this help you?
- 17Checking overflow ports and pan backupsDid this help you?
- 18Looking for frost or melting ice from the A-frameDid this help you?
- 19Shutting off the AC unit immediately when the strange noise occursDid this help you?
- 20Waiting for a few minutes before attempting to restart the unitDid this help you?
- 21cleaning the coilsDid this help you?
- 22checking decibel levelsDid this help you?
- 23Shutting the system off until a professional can inspect itDid this help you?
- 24Replacing basic consumable parts like capacitors and contactors independentlyDid this help you?
- 25turn off the ac and leave the fan onDid this help you?
- 26Testing the unit in fan-only mode to isolate the issue to the compressorDid this help you?
- 27Replacing the fan bearingDid this help you?
- 28Buying a replacement unit and swapping it outDid this help you?
- 29Apply pressure to the top of the AC unit with your hand to stop the vibration.Did this help you?
- 30Loosen the screws slightly on top of the condenser cage.Did this help you?
- 31calling the landlord to handle the repairDid this help you?
- 32Shutting the unit off for an hourDid this help you?
- 33Calling an HVAC professional for diagnosisDid this help you?
- 34Contacting the landlord for a maintenance visitDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“AC was set to 70° but it was at 76° when I found it. AC was making this noise so I shut it off for about an hour. When I replaced the filter and turned it back on it was still making this noise.”source ↗
“Our old unit finally gave out yesterday and sounds like a jet engine taking off every time the compressor kicks on. Since it is right in the main bedroom, we really need something quiet that can actually cool down about 400 square feet without driving us crazy at night.”source ↗
“The other one works fine, but this one is so incredibly loud. I have opened it up and tightened every screw, but it still sounds like a plane taking off. Any advice on how to address this?”source ↗
“I recently noticed that there is a constant noise coming from Evaporator and/or refrigerant line.”source ↗
“It seems to constantly cycle, and change its tone, almost how a shaving cream can would sound different as it gets close to empty.”source ↗
“My Rheem certified tech says it's normal, but I can hear this a floor away, and this noise was not there when the system was new.”source ↗
“As of last night it sounds absolutely awful, I have never heard it sound like this in the 3 years of owning it”source ↗
“this sound is exactly what jumpscared me last night that made me jump out my skin and get out of bed to turn off the A/C off as I knew that was definitely not a good start up sound.”source ↗
“I’m an electrician and have been able to keep my AC unit running replacing a capacitor and contactor…now months later is making this noise. Please help if you can!”source ↗
“Just changed my capacitor few weeks ago. I did notice my condenser sounds louder these days.”source ↗
“what I would assume is the fan or unit (not an expert) turns on once an hour for about 5-10 minutes emits a loud consistent noise and then goes back to normal.”source ↗
“My AC works as it should but the noise is so loud and wakes me up throughout the night.”source ↗
“It has been a month since the repair in the same noise as happening again, but louder.”source ↗
“The only way to get the noise to stop is to fully turn off the AC switch.”source ↗
“Just got home and noticed the AC unit making an insane amount of noise.”source ↗
“Air was blowing in the house but the unit wasn’t kicking on at all — usually it kicks on right away so I’m assuming that’s a bad sign.”source ↗
“It’s not full of water, I drained it. Is it hitting something?”source ↗
“It’s one of those U-shaped ones. The weird thing is, it is tilted back enough, but the outside is bone dry. Meanwhile the front of it is just POURING water.”source ↗
“Very odd. Can hear it throughout the condo. Cannot be normal for a system that is supposed to be very quiet.”source ↗
“Last night when I was sleeping the compressor started vibrating very loudly and would turn off every 3 minutes.”source ↗
“this morning it’ll make this intermittent humming noise but won’t shut off.”source ↗
“I had a new mini-split installed this summer and now that I've switched it to heat mode, it's making a loud popping/cracking sound about every minute or two. It's quite annoying as I can't sleep well because of it.”source ↗
“I noticed the unit has quite a bit of play if I grab it and try to lift it slightly”source ↗
“Is this normal for the mounting bracket to have this much play?”source ↗
“My HVAC Outdoor unit is now making this sound when thermostat signals it to turn on. It's a little bit loud.”source ↗
“Seems like it got louder recently but wanted to see if this sounds normal.”source ↗
“My line seems to have frost on it and making an strange hissing sound. I live in an apartment. Any notes I should tell the landlord for proper fix?”source ↗
“So yeah when I put pressure on it with my hand it does sound more quiet”source ↗
“Heard the condensate drain line draining loudly for about 20 minutes, took a video with the draining slowed a little bit such that it’s not audible, but you can still see a good amount of water coming out.”source ↗
“Has anyone seen this before? Is it normal or excessive drainage? Of course I’m noticing this on a late Friday afternoon and I would love to avoid any emergency HVAC calls if possible… $$$$”source ↗
“Just curious why my HVAC is screeching after a few minutes of running. 🥴 I have no interest in trying to fix it myself…calling my landlord in the morning, but just curious. It’s so loud!”source ↗
Where this came up
People with this problem also raised
- 8Why is my AC making a loud noise after changing thermostats?
- 3Lights flickering when the AC turns on
- 3Loud noise from passenger dashboard when turning air to max
- 6Why does my HVAC condensate pump sound like a jet engine?
- 3Is it safe to drive with a noisy AC compressor pulley?
- 3How to cool down a house when the AC breaks during a heatwave