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How to Diagnose & Repair Tight or Seized Air Conditioning Compressors InspectAPedia®  -     Diagnosing tight or seized air conditioner compressors How to re-start a tight or seized air conditioning compressor Air conditioning compressor hard-starting

This chapter of "How to Inspect the Central Air Conditioning or Cooling System" discusses the Diagnosing Tight or Seized Air Conditioning Compressors and how to re-start a tight air conditioning compressor. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2010 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.

Diagnosing Tight or Seized Air Conditioning Compressors

Sometimes a compressor may be internally damaged or worn in a way that makes the piston(s) run tight in the cylinder(s) rather than loose and worn (loose or worn air conditioner compressor diagnosis is described at LOST COOLING CAPACITY).

A tight or seized air conditioner compressor might occur, for example, if the compressor ran while low on oil. Or perhaps if the compressor is old and has not been run in some time. The A/C compressor may refuse to start at all, or may be hard-starting depending on when it last ran and what it's temperature is.

A "hard starting" "tight" air conditioner compressor will probably draw excessive current (Amps) during startup, so that measurement may be used as part of the diagnosis of this problem.

Re-Starting a Tight or Seized Air Conditioner Compressor

The service technician may try re-starting a hard-starting or tight air conditioning compressor by trying to move the motor backwards and forwards.

If the compressor can be freed up enough to start at all and the oil level is made correct, the technician may install a "hard start kit" such as we introduced at HARD STARTING and see  CAPACITORS for HARD STARTING MOTORS for photos, wiring diagram, and installation instructions for air conditioner compressor, fan, blower, refrigerator motor, freezer motor, or other electrical motor starting booster capacitors.

If these steps work the compressor may continue to be used. If these steps do not get the tight or seized compressor running, it needs to be replaced. But even if these steps do work, the compressor has probably been damaged and you should not count on its long future life before it needs to be replaced.

How We Measure Amps or Current Draw at the Air Conditioner Compressor

Basic air conditioning compressor operation check: after the air conditioning system compressor/condenser unit has been running long enough to stabilize at its normal operating temperatures and pressures (typically 10 to 20 minutes), the service technician may measure the compressor's current draw in Amps using an ammeter or amp meter or multi-tester and appropriate connections.

The current draw in AMPS is compared with the unit's specified FLA or "full load amps" found on the data tag or in the service manual for the unit. Remember that the FLA number includes the current draw of not only the compressor motor itself but also the condenser fan motor as well as the compressor motor base heater if a heater element is installed and operating.

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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.

AIR CONDITIONING & HEAT PUMP SYSTEMS
AGE of AIR CONDITIONERS & HEAT PUMPS
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER UNITS
APPLIANCE EFFICIENCY RATINGS
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - Air Conditioning "How To" Books
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
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DUCT SYSTEMS
DUCTS - Asbestos
DUCT SYSTEM DEFECTS
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
ENERGY SAVINGS in BUILDINGS
EVAPORATIVE COOLING SYSTEMS
FAN AUTO ON Thermostat Switch
FAN CONVECTOR HEATERS - HYDRONIC COILS
HEAT LOSS (or GAIN) in BUILDINGS
HUMIDITY LEVEL TARGET
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
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
SWAMP COOLERS
THERMOSTATS
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS
Air Conditioning "How To" Books

• 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 Jon Bolton, an ASHI, FABI, and otherwise certified Florida home inspector who provided photos of failing Goodman gray flex duct in a hot attic.
• 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.).

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.
• Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.
• Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
• Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
• "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]
• Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
• 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.).
• ...

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