How to Evaluate Air Conditioner Compressor Noises InspectAPedia® -
How to diagnose & repair air conditioning compressor noises
Air conditioner buzzing may be just a loose part
Air conditioner humming, clanking, buzzing noises can indicate a minor or a serious problem - it depends ...
Air conditioner compressor defect diagnosis
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This chapter of "How to Inspect the Central Air Conditioning or Cooling System" 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.
If your air conditioning system has lost its cooling capacity or won't start see REPAIR GUIDE for AIR CONDITIONERS. See How to determine the cooling capacity of air conditioning equipment if the system seems to be working but is inadequate to cool your building.Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
COMPRESSOR NOISES - How to Diagnose Air Conditioner Compressor Noises
If you hear unusual noise at the air conditioning system, these compressor sounds could indicate the need for a simple service and adjustment requirement.
But air conditioner compressor noises might also mean that you face an upcoming costly
repair involving replacement of the compressor itself. You should have the system checked promptly by an air conditioning service technician.
The following is a list of air conditioning compressor noises and what they may mean about
the operation, condition, and remaining life of the cooling system equipment.
Loose hardware: Air conditioner compressor noise could be due simply to loose hardware such as a loose shipping bolt, tubing, or a broken spring. Does the
noise sound like a metallic rattle? A visual inspection for loose hardware may help diagnose this condition.
Sometimes a shipping bolt may have been left in the unit and could be the source of a rattle. Loose refrigerant tubing or a bend in
tubing that carries it too close to the air conditioner frame or case can lead to rattling that is easily corrected with a careful
bend.
BEWARE of both
the chance of electrical shock and of injury from moving compressor
parts like the cooling fan which can easily chop off a finger. Homeowners should not attempt to open, disassemble, or repair an air conditioner compressor as
special training and safety procedures are needed to avoid injury.
Refrigerant floodback: Air conditioning compressor noise could also be due to refrigerant liquid "floodback" into the compressor crankcase.
If this is the problem the noise will
appear only at the interval of compressor start-up. That's why it's useful for the inspector or service technician to be right at the compressor unit when the
air conditioning system is first turned-on. If this is the problem, a low cost repair might work: a crankcase heater can be installed to address this defect.
Oil leaks: Another source of cooling system compressor noise is a low oil condition in the compressor unit. Low oil may be diagnosed perhaps by observing
evidence of compressor oil leakage on or around the unit. Modern residential air conditioning compressors are usually a hermetically sealed unit; it would be
abnormal to ever see oil loss around this equipment. (But don't mistake spilled oil from lubricating an electric motor or cooling fan
bearing for a refrigerant or compressor oil loss.)
Checking air conditioner oil level: A few residential air conditioning compressors and many commercial systems provide an oil
sight glass to permit a visual check of oil levels. On those units, when the compressor is running the oil level on the sight gauge should read 1/2 to 3/4 full.
If adding oil to a commercial unit, be careful not to add too much. Both too much or too little oil can cause compressor noises. On a residential compressor which is usually a hermetically-sealed motor, it is
not possible to see the oil level nor to add oil.
Normal squeals Normal air conditioner compressor squealing: Some compressors emit a high pitched noise during normal operation or just at startup.
Clanking or banging air conditioner compressor noises, at least the costly ones, are usually due to a loose connecting rod, piston pin, crankshaft, or other internal part. Since compressors on most
modern commercial and residential air conditioning systems are a sealed unit, the only repair is to replace this (costly) part.
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Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects"
section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and
home inspection educator.
Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Thanks to Diaz, Domingo I. CIV NAVAIR Bldg.2118, rm. 131: domingo.diaz@navy.mil
- Ming Diaz, Great Falls, MD for editing help with the text about discharging air conditioning compressor capacitors - 3/07 DF]
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend)
Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
More Information on Building Diagnostic Inspections and Repairs
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