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How to diagnose loud start, popping, rattling, rumbling, running water sounds or just plain silence at an air conditioner or heat pump.
Air conditioner or heat pump noise diagnosis & cure: this air conditioning repair article discusses the diagnosis and repair of air conditioning compressor noises which range in importance from normal (if annoying squeaks and squeals, to rattling loose bolts and hardware, to costly compressor damage indicating air conditioning compressor or A/C compressors at or near end of their life.
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HVAC Noise Group 4: loud start, popping, rattling, rumbling, running water sounds at an air conditioner or heat pump. Also "no noise" or "silent" equipment
The following HVAC noise descriptions are a continuation from the article beginning at NOISES, HVAC SOUND DESCRIPTIONS
I had problems with my central unit freezing up and dripping water on my fan motor. Idecided to have a technician change out my coil inside. When he left my central unit outside starting making noises I never heard before.
My air conditioner kicks on inside first then after a couple of minutes it tries to kick on outside , it makes a loud noise then it runs finally and quiet like a central unit should run outside.
What is causing this all of a sudden? We never had problems until he changed my coils out..not calling him back to my house. - Bruce McCann
Reply: Indoor coil freeze up vs outdoor sounds??
I am not clear on why a coil freeze-up indoors would lead to changing the outside coil - maybe low refrigerant or improper high side vs low side pressures? In any case, I would indeed give the service tech a call, tell him or her what you are observing, and give the technician an opportunity to return, see what's wrong, and fix it. Most technicians want their work to be correct and successful. Let us know what you're told - it will surely help other readers.
Question: a/c condenser unit sounds like a popcorn machine only when going off
Question: I just had a new compressor installed outside two weeks ago. In the last few day this unit has emitted loud intermittent "popping" sounds like firecrackers that keep us and the neighbors from sleeping! Cannot see anything obvious and not sure if related to recent repair. It is not a regular pattern or a metallic sound. Recorded for our a/c guy and he thinks a wire is loose and the sound is an electrical contact sound. Ideas? Thanks. Mike C. 9/12/11
Watch out: an A/C or heat pump compressor motor that is receiving liquid refrigerant on the suction or intake side of the system can make a popping noise or popcorn noise - and is at serious risk of becoming damaged or destroyed. Liquid refrigerant should be found only on the output side of the compressor/condenser unit not at the compressor intake.
Causes of "liquid flooding" of an HVACR compressor include improper refrigerant charge (too much refrigerant) or a malfunctioning refrigerant metering device at the cooling coil. You should shut off the system immediately and leave it off until an experienced HVAC service tech has diagnosed the problem, hoping that we might avoid destroying the compressor motor.
Other causes of popping or knocking sounds in air conditioners or heat pumps - knocking sounds can mean a bad motor bearing, bad motor mount, or on occasion, a spinning fan blade hitting a component in either the air handler or outside in the compressor/condenser unit.
In automotive A/C systems, condensate dripping onto a hot exhaust manifold can also cause a "popping" sound in some designs.
Watch out: electrical shorts and loose wires can also make a "popping" sound at any electrical equipment. Turn off the equipment to reduce the risk of a fire or dangerous electrical shock.
Any readers with other suggestions please post a "popcorn noise" comment.
Question: We just noticed our outdoor compressor unit running noisier than usual. Not exactly a rattling noise but a louder than usual buzzing type sound. It was constant. So we turned off the AC at the thermostat. and looked around the unit to see if we could see anything unusual. Didn't really know what we were looking for, but didn't see anything unusual.
About 15 minutes later we turned the AC back on and it took about 10 minutes to "kick in" at that time there was only a low humming sound from the compressor. The fan never started. We let it run for about 15 minutes and there was no change. Just prior to noticing the noise in the first place, we realized that it seemed hotter than it should be in the house and the air blowing out of the registers was room temp, not cool. - Kim
Well, I read the story below about the person who was told to rinse off their external coils. so we gave that a try while the AC was turned on. After about 3 minutes of spraying with the garden hose it started up. It sounded smooth, too, no strange noise, except for the water spraying off the fan blades. YAY!
Well Darn it. When we woke up it wasn't running again. I got it started again by spraying with the hose. But the whole system doesn't seem to be blowing as cold as it used to. And my guess is on the next cycle the compressor wont start on it's own again. - Kim
Reply: common sources of HVAC rattling noises
Rattles at HVAC systems: look for loose hardware, loose fan blades, pulleys, or motor mounts; also possibly loose ductwork. We have seen rattling traced to loose motor mounts, loose motor bearings, loose equipment covers, refrigerant piping vibrating against a surface, and loose fan blades impacting or ticking against other equipment compnents or surfaces.
Watch out: a sort of rattling sound may be made by an air conditioner or heat pump (or other HVACR equipment) compressor motor if the refrigerant level is too high - that is if the system has been overcharged. This condition can damage or even destroy the compressor very quickly. See EFFECTS of OVER CHARGING of REFRIGERANT -
Refrigerant floodback noises - running water or gurgling sounds in the refrigeration piping
I have a 4 ton heat pump that hisses when it shuts down in 40* weather. The frig. lines run in the wall near bedroom. Sounds like freon running back to or from compressor, Only in heat cycle. - firstname.lastname@example.org 12/11/11
Question: Just this morning I noticed when my heat unit/pump was running it sound as if water was draining through pipes. (The out side connections to the pump/inside unit run over head in my laundry room) So far there's been no other issues. Any idea what this could be? Should I be concerned? Once the heat shuts off this draining sound quits. - Ruth 1/25/12
Reply: causes of running water or burbling gurgling sounds in HVAC equipment
Refrigerant floodback noise can occur at any time not just at startup. A severely overcharged system compressor can have floodback when running and this can lead to compressor failure from oil being flushed from compressor or broken valves in reciprocal compressors. - Tommy 1/15/2012
Ruth, also check for running water sounds traced to drain piping that receives air conditioner or heat pump condensate from a condensate pump. Because the condensate pump only runs when its reservoir is filled, the pump on-off cycle will be irregular, but the pump may be sending water into a building drain that, because of its material (plastic) and location (not through sound-insulated space) could show up as a running water or gurgling sound.
Bubbling in the refrigerant piping is discussed at REFRIGERANT LEAK REPAIR and may indicate a refrigerant leak, though bubbling sounds on split systems at the indoor wall unit may be normal for some products.
Repetitive or Cyclic Vibration Sounds
AC has an intermittent loud vibration that lasts about 15 seconds and goes away.
It occurs about every 30 seconds or so. We just had to have freon installed because the unit was running but never able to achieve the set point. We keep it at 76, so it wasn't like we were straining it. My husband is checking to see if it's level right now since we read a comment that out of level can lead to vibration and from there to a refrigerant leak. We obviously had a leak since the gas was at less than half of its required level. - Rebecca
Reply: Cycling or repetitive noises in HVAC compressors
Rebecca: there are several failures that can cause a frequent cycling noise in HVAC compressors such as
Silent or normal noise A/C Compressor - still to be replaced?
My AC is blowing warm air. Everything is in working order except the technician found a leak from one of the tubes coming out of compressor closer to the unit itself. He told me that the whole compressor would have to be changed. Is it true? The compressor sounds normal. - Ehab
Reply:blowing warm air ... lost refrigerant; I answered this question just a minute ago - maybe on our refrigerant gauges page?
Ask him/her why you need a new compressor instead of a fix of the refrigerant leak and either a recharge, or if your refrigerant is an obsolete R12 or R22, why not use a substitute refrigerant?Note that a compressor may sound normal or even close to silent but be running but may not be pumping refrigerant. If this is the case the unit has broken internal parts and needs replacement.
A symptom would be no refrigerant pressure difference between high side and los side lines even with the compressor "running".
Continue Reading more Noise Descriptions at noise group 5 beginning with SCREAMING from A/C or heat pump system
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