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• Air conditioning compressor noises
• Air conditioner compressor defect diagnosis

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. © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left.

Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links 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.

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.
• Humming air conditioning compressor motors, particularly if the motor is slow to start or does not start at all, may indicate that the starting capacitor needs replacement.
• 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.

AIR CONDITIONING SYSTEMS
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
  Indoor A/C Components
  Outdoor A/C Components
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER UNIT
BACKUP HEAT for HEAT PUMPS
CLEANING & Legionella BACTERIA
COMPRESSOR & CONDENSING COIL
  BURNED-OUT COMPRESSOR
  CAPACITORS for HARD STARTING MOTORS
  CONDENSING COIL FINS, SUPPORT PADS
  HARD STARTING COMPRESSOR MOTORS
  INSTALLATION ERRORS, COMPRESSORS
  MOTOR OVERLOAD RESET SWITCH
  NOISY COMPRESSOR UNITS
  PRESSURE READINGS, COMPRESSOR
  REPLACING A COMPRESSOR
  TIGHT or SEIZED AC COMPRESSORS
CONDENSATE HANDLING
CONTROLS & SWITCHES
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
  FROM MODEL #
  FROM EQUIPMENT RLA #
  COOLING RULES OF THUMB
COOLING COIL or EVAPORATOR COIL
DATA TAGS on AIR CONDITIONERS
DUCT SYSTEMS
DUCTS - Asbestos
DUCT SYSTEM DEFECTS
DUCT INSULATION, Asbestos Paper
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
FAN AUTO ON Thermostat Switch
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LOST COOLING CAPACITY
  What to check first
  Compressor failure diagnosis
  Duct & Air Handler diagnosis
MOTOR OVERLOAD RESET SWITCH
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
  Air Conditioning System Temperatures
  Instruments Used to Measure A/C Temperatures
  Procedures for Making Temperature Measurements
REPAIR GUIDE for AIR CONDITIONERS
REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS
  REFRIGERANT LEAK DETECTION
  REFRIGERANT LEAK REPAIR
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
  OPERATING CONTROLS
  SAFETY CONTROLS
THERMOSTATS
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS
Air Conditioning "How To" Books


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AIR CONDITIONING SYSTEMS
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
  Indoor A/C Components
  Outdoor A/C Components
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER UNIT
BACKUP HEAT for HEAT PUMPS
CLEANING & Legionella BACTERIA
COMPRESSOR & CONDENSING COIL
  BURNED-OUT COMPRESSOR
  CAPACITORS for HARD STARTING MOTORS
  CONDENSING COIL FINS, SUPPORT PADS
  HARD STARTING COMPRESSOR MOTORS
  INSTALLATION ERRORS, COMPRESSORS
  MOTOR OVERLOAD RESET SWITCH
  NOISY COMPRESSOR UNITS
  PRESSURE READINGS, COMPRESSOR
  REPLACING A COMPRESSOR
  TIGHT or SEIZED AC COMPRESSORS
CONDENSATE HANDLING
CONTROLS & SWITCHES
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
  FROM MODEL #
  FROM EQUIPMENT RLA #
  COOLING RULES OF THUMB
COOLING COIL or EVAPORATOR COIL
DATA TAGS on AIR CONDITIONERS
DUCT SYSTEMS
DUCTS - Asbestos
DUCT SYSTEM DEFECTS
DUCT INSULATION, Asbestos Paper
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
FAN AUTO ON Thermostat Switch
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LOST COOLING CAPACITY
  What to check first
  Compressor failure diagnosis
  Duct & Air Handler diagnosis
MOTOR OVERLOAD RESET SWITCH
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
  Air Conditioning System Temperatures
  Instruments Used to Measure A/C Temperatures
  Procedures for Making Temperature Measurements
REPAIR GUIDE for AIR CONDITIONERS
REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS
  REFRIGERANT LEAK DETECTION
  REFRIGERANT LEAK REPAIR
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
  OPERATING CONTROLS
  SAFETY CONTROLS
THERMOSTATS
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS
Air Conditioning "How To" Books

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