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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 UNIT
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - Air Conditioning "How To" Books
CLEANING & Legionella BACTERIA
COMPRESSOR & CONDENSING COIL
CONDENSATE HANDLING
CONDENSING COIL
CONTROLS & SWITCHES
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
DATA TAGS on AIR CONDITIONERS
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
DEFINITION of Heating & Cooling Terms
DEW POINT TABLE - CONDENSATION POINT GUIDE
DUCT SYSTEMS
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
FAN AUTO ON Thermostat Switch
HEAT LOSS (or GAIN) in BUILDINGS
HUMIDITY LEVEL TARGET
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LOST COOLING CAPACITY
  What to Check First
  A/C Flow Too Weak
  A/C Filter Problems
  A/C Compressor Problems
  A/C Off - Condensate Pan Switch
  A/C Cooling Coil Icing
  A/C Not Dehumidifying
  A/C Air Duct Problems
  Air Conditioner Won't Start
  Air Conditioner Refrigerant Problems
  Blower Fan No Start / No Stop
  Compressor Diagnosis: Diagnose & Repair
  Cooling Capacity of the Duct System
  Repair Guide Master List
MOTOR OVERLOAD RESET SWITCH
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
REPAIR GUIDE for AIR CONDITIONERS
REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
THERMOSTATS
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS on A/C SYSTEMS

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Photograph of client using tissue to look for air conditioning air flow

How to Diagnose & Repair Loss of Air Conditioner Cooling Capacity or an Air Conditioner that is Not Working
AirCondAPedia ^©

How to diagnose & repair loss of air conditioning cooling capacity or has stopped working

Air conditioner repair checklist: before calling an air conditioning service technician check these items

Air conditioner compressor defect diagnosis

How to diagnose and fix an air conditioning system that is not working

Our site offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at inspect-ny.com/appointment.htm.

This article discusses the how to diagnose and correct air conditioning problems like lost or reduced air conditioner cooling capacity or an air conditioner that won't start. If not enough cool air is provided by your air conditioner, or if the air temperature is not cool enough, or if you just can't get your A/C unit running, this article helps diagnose and correct the problem with step by step things to check and links to more detailed explanation when you need it. We provide links to other air conditioning system diagnostic articles too.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website.

What to Check First if the Air Conditioner Output is Inadequate

These Simple Checks May Enable Inexpensive Repair of Lost Cooling Output from an Air Conditioner

Before ordering an expensive air conditioner service call to restore lost cooling capacity, here are a few simple steps to perform. Some of these can be done by any homeowner, others may require a bit more expertise.

Air Conditioner Air Flow Too Weak

Air Conditioner Blower fan unit not moving enough air: too little air coming out of your air conditioning ducts?

Check the condition of the blower unit: if it's dirty the blower may be spinning but not moving much air. See DIRTY A/C BLOWERS for details.

Dirty filters or iced coils or crimped or disconnected air ducts can also cause loss of cool air or too little cool air coming out of supply registers.

These items are addressed below in this air conditioner diagnostic guide. Also see DIRTY COOLING COIL and FROST BUILD-UP.

Sketch courtesy of Carson Dunlop
Air flow that is too slow for any reason (such as a dirty filter or dirty blower fan assembly blades) can cause first, air temperatures that are abnormally low coming out of the air conditioner, and eventually a reduction in air flow as coil ices over. See A/C Cooling Coil Icing.

Air Conditioner Filter Clogging Problems & Weak Cool Air Flow

Clogged Air Conditioner filters can lead to lost cooling capacity first, because the clogged filter reduces the air flow through the system, meaning that you'll feel less air flow at the supply registers than was previously present.

See AIR FILTERS for HVAC SYSTEMS for details.

Air Filter problems: not enough air coming out of air conditioning ducts? Check for a very dirty, blocked air filter or blower fan. See AIR FILTERS for HVAC SYSTEMS and AIR HANDLER UNIT

Air Conditioner Compressor Problems

Compressor problems - Air Conditioner Compressor: problems such as an aging air conditioner compressor motor that is at or near the end of its life may be unable to properly compress the returning refrigerant gas to a sufficiently high pressure. A service technician will need to evaluate and test the system and if needed, replace the compressor.

Since this is a costly repair, be sure to ask why the compressor failed and to correct any underlying cause (such as low voltage). Variations in line voltage can lead to improper compressor operation and loss of cooling output.

See COMPRESSOR CONDENSER for diagnostic details. If you have a hard-starting air conditioner compressor that "hums" but doesn't start, it may be possible to get more life out of the compressor motor with a simple starting capacitor (rather than a costly whole new compressor motor.) See A/C CAPACITORS.

Air Conditioner Off Due to Condensate Pan Switch

Condensate pan switch lockout: an attic or other air conditioner air handler condensate drip tray or drip pan located under an air handler is installed to catch air handler condensate leaks if the normal condensate drain system fails. Some condensate pans have their own separate overflow drain (a proper installation) or share their drain with the normal condensate drain (an improper installation).

But on some air conditioning air handlers the installer may provide a condensate overflow pan switch rather than a separate pan drain line. In this installation the switch is designed to turn off the air conditioning system if it finds condensate water in the overflow pan. The idea is to shut down the air conditioner before there is a more costly leak into the building insulation or ceiling.

So if your air conditioning system seems to be normal in all other respects but it simply won't turn on, check for a flooded condensate pan or a defective condensate switch. See DRIP TRAY DEFECTS and also Use of float switches on air conditioning condensate overflow pans

Air Conditioner Cooling Coil Icing Problems

Ice blocked air conditioning cooling coil (C) Daniel Friedman

Cooling Coil Ice-Up on the air conditioner air handler or evaporator coil: A second result of the reduced air flow due to a dirty air conditioning filter can cause the evaporator coil (the cooling coil) in the air handler to become blocked by ice, stopping or significantly reducing cool air output from the system.

A visual inspection of the cooling coil in the air handler can quickly show whether or not it's ice-covered. If the coil is iced-up and blocked, turn off the cooling system entirely until the ice has all evaporated and cleared. Be sure that your condensate drain is not blocked and that the water from melting ice will be properly disposed-of.

If you replace all dirty filters on the system and remove ice from an iced coil and the coil ices up again when the system is turned back on, you may have the next condition in this list.

For a detailed discussion of air conditioner or other refrigeration (or dehumidifier) cooling coil ice-up diagnosis and cure, see Air Conditioning Cooling Coil or Evaporator Coil Ice-up at FROST BUILD-UP

Air Conditioning System Dehumidification Problem Diagnosis & Cures

Air Conditioning Dehumidification Problems: air conditioning system cools but does not dehumidify the room. The most common cause of inadequate dehumidification by an air conditioning system is the installation of a cooling unit which has too much capacity, or is "over-sized" for the space it is being used to cool. What happens is simple:

If an air conditioning compressor unit is oversized (too many BTUH of cooling capacity) what happens is it cools the room so quickly that the system does not move enough total volume of air across the cooling coil to remove much moisture before the room temperature has dropped to the A/C cut-off point.

In other words, an air conditioner needs to run longer, and move more total volume of air through itself to drop room humidity than it does to just cool the air.

Key Air Conditioning Inadequate Dehumidification Symptom: If your cooling system is otherwise working normally, and it cools the room temperature quickly but the room humidity stays high, an over-sized unit is likely to be the problem.

Cures for inadequate dehumidification by an air conditioner

First make sure that the equipment is operating properly: is it cooling - check that temperatures are dropping normally when the system is running.
Check that there is not an abnormal moisture source such as leaks into the building or its wall or ceiling cavities from any other source. Check to see if the condensate drain from the air conditioner is producing water. If you see lots of A/C condensate dripping out of the system condensate drain but room humidity is still high, we suspect that there may be an abnormal humidity source. At the end of this list we discuss adding additional dehumidification capacity.
Adjust the A/C unit controls to increase dehumidification: discuss with your HVAC service technician whether there are technical changes that might be made to fan speed or other controls that might improve A/C unit dehumidification. We're doubtful there is much mileage in this but it's worth asking.
Increase the cooling load on the installed air conditioner by making it cool a larger area - like maybe leaving the doors open to other rooms - which we doubt is suitable in most cases. Our photo (above left) shows a wall mounted air handler from a Sanyo™ split system air conditioner that was not adequately dehumidifying the bedroom where it was installed, even though the room was cold enough to hang meat. The occupants experimented with leaving the bedroom door opened, as the rest of their home did not have air conditioning. That proved just enough to cause the system to dehumidify beautifully.
Adjust the building HVAC system ductwork: if a non-dehumidfying central air conditioning system (as opposed to a window unit or a wall-mounted split system unit) is otherwise working well, it may be possible to adjust its load and thus improve its dehumidification by making changes in the duct system, such as increasing the return air to the air handler from additional building areas.
Replace the oversized air conditioner: Unfortunately the most likely fix for an A/C system that is not dehumidifying may be an ugly one - either replace the unit with one that is properly matched to the size of the area to be cooled
Select an A/C unit of the proper size. See AIR CONDITIONER BTU CHART for the data useful to do this. Whoever selected and installed the air conditioning unit needed to relate the room size to the AC capacity. Also see COOLING RULES OF THUMB to guesstimate how many tons or BTUs of cooling a building needs and see RATED COOLING CAPACITY to determine the cooling capacity of existing air conditioning equipment.
Add supplemental dehumidification. For wet conditions that exceed the capacity of the air conditioner itself, or when you require both unusually low temperatures and further dehumidification (such as a seed storage facility described by one of our readers), it may be necessary to add a separate free-standing or portable dehumidifier to the system to reach the temperature and humidity targets you need.

In an area of our forensic laboratory we use a Sears® dehumidifier, model 580.54501 - 50 pint (also available as 580.54701 - 70 Pint Low Temp) (cost about $200.). The Sears portable dehumidifier instruction manual (Part# 3828A20803B) confirms on p.7 that the humidity control can be set anywhere between 35% and 70%. You can also adjust the fan speed (low / high) and also set an on-off cycle period of 3 hrs or 6 hrs.

Operating a dehumidifier (which uses the same technology as an air conditioner) will have a side effect of pumping a little heat into the dehumidified area - the output side of the dehumidifier produces air that is warmer than its input side. Depending on the size of the area being conditioned, that added heat might help compensate for an air conditioner that was a little oversized for the space.

Air Conditioning Air Duct Problems

Duct problems: Damaged Air Conditioning Ducts such as ducts which have been improperly routed and are crimped, crushed, or have excessive bends can reduce cool air flow in an otherwise properly functioning system.

One client had us drive a considerable distance to repair her apartment's central air conditioning system after having had several unsuccessful service calls.

Apparently no one had managed to get into a rather tight and hard-to-enter attic crawl space where the cooling ducts were routed. We found that the main cooling duct had become disconnected.

The attic was nice and cool but no cool air was being blown into the living area. Check the condition of the duct system for blocked ducts, loose leaky connections, closed dampers, crimps and bends, before calling your service technician.

See DUCT SYSTEM DEFECTS for details of various A/C duct problems and how to detect and correct them.

Air Conditioner Won't Start

Electrical problems: air conditioning system won't start: it may sound silly, but is the air conditioner turned on?

Has the cooling thermostat been set to "cool" and the temperature set below ambient room temperature?

Do both the outdoor compressor/condenser unit and the indoor blower fan/evaporator coil unit have electrical power?

Has the air conditioning electrical wiring been physically damaged or cut? Photo courtesy of Tim Hemm.

Are the power switches on at these units, are the fuses good, are the circuit breakers in the "on" position, and is the thermostat set correctly? See CONTROLS & SWITCHES and THERMOSTATS for some diagnostic tips.

Air Conditioner Refrigerant Problems

Refrigerant problems: Improper air conditioner refrigerant charge - too little, too much, too leaky: an air conditioner system which has lost some (but not most) of its refrigerant will sometimes run too cold at the evaporator coil, leading to coil icing and loss of cool air delivery in the home.

If the filters are clean and the coil ices-up this condition may be present. A service technician will need to evaluate and test the system and if needed, adjust the refrigerant charge.

Also see REFRIGERANTS and A/C REFRIGERANT LEAK DETECTION for more details.

Low refrigerant level in the air conditioning system: Watch out for refrigerant leaks that lead to a repeat of this problem. An air conditioner or refrigerator is a sealed system that should not normally "use up" refrigerant. If the cooling system is low on refrigerant because it has a leak, it is much smarter to find and fix the leak than to simply keep adding refrigerant. If you keep adding refrigerant to a cooling system you're leaking possible contaminants into the environment as well as wasting money.

Abnormally low output air temperature: A refrigerant leak in an air conditioning system may show up first as abnormally low system output air temperature, followed by rising air temperatures, followed by just plain old warm air coming out of the system, as the amount of refrigerant that has been lost increases.
Loss of most refrigerant from an air conditioning system means that the cooling coil will not get cool at all.

Abnormally high output air temperature: A service technician will need to evaluate and test the system and if needed, find and fix the refrigerant leak, evacuate the system, and install the proper refrigerant charge. See A/C REFRIGERANT LEAK DETECTION for diagnostic details.

Don't keep adding refrigerant. Refrigerant leaks should be found and repaired. It may be easier to keep adding refrigerant, and sometimes a refrigerant leak can be hard to find, but a proper repair is to find an fix the refrigerant leak, not just to keep adding refrigerant. See REFRIGERANT LEAK DETECTION. See A/C REFRIGERANT LEAK DETECTION for details.
Improper refrigerant charge - too much can also lead to improper air conditioning system operation and in some cases can damage the compressor (called liquid-slugging the air conditioner compressor). A service technician will need to evaluate and test the system and if needed, adjust the refrigerant charge. In this case the cooling coil is probably not going to ice-over, it just won't get cool.

Air Conditioner Won't Start - Blower Fan Will Not Turn on or Will Not Turn Off

Thermostat problems: Air Conditioner Thermostats:

Air conditioner won't turn on, or fan won't turn on or won't turn off.

See THERMOSTATS for a discussion of how air conditioner thermostats work and how the air conditioner blower fan controls work.

Air Conditioner Compressor Diagnosis: How to Diagnose & Repair an Air Conditioner Compressor Which has Lost Cooling Capacity

A compressor which appears to have lost cooling capacity can be diagnosed by a service technician who can connect the appropriate test gauges to the system. Lower than normal discharge pressure and higher than normal suction vacuum will indicate this problem.

But before assuming that something is wrong with the air conditioning compressor, some basic investigation is in order. Unless there is an obvious indication of a compressor problem (noise, hard starting, compressor won't start), the service technician, to be thorough and economical, will inspect the system in an order, checking the easy and least-costly problems first, such as presence of electrical power, proper setting and operation of system controls, condition of filters, condition of duct work, operation of blower fans, before moving on to check the compressor itself by looking at the air conditioner operating temperatures, pressures, and current draw in Amps.

Cooling Capacity of the Air Conditioning Equipment

The cooling capacity of an air conditioning equipment refers to the ability of the compressor/condenser (usually outside) and the air handler/evaporator (usually inside) to deliver cool air to the occupied space.

Briefly, the compressor/condenser draws refrigerant gas from the building air handler, compresses it and cools it back to a liquid refrigerant, and the air handler/evaporator coil permits liquid refrigerant to evaporate inside a cooling coil, across which the fan blows building air to cool and dehumidify it.

The particular combination of this equipment has a cooling capacity, usually rated in BTUh or thousands of BTU's of cooling capacity per hour, documented on equipment data tags discussed above at "RATED COOLING CAPACITY" - see AIR CONDITIONER BTU CHART and see COOLING RULES OF THUMB to guesstimate how many tons or BTUs of cooling a building needs and see RATED COOLING CAPACITY to determine the cooling capacity of existing air conditioning equipment.

Air Conditioner Long "on" cycle and Insufficient Cooling - Loose or Worn Compressors

A longer than normal "on" cycle combined with little or no cool air conditioner output could be due to an inefficient air conditioning compressor or one which has lost its ability to "compress" the refrigerant due to internal wear. This condition can be diagnosed by an air conditioning service technician who will install air conditioning manifold gauges onto the system to check the compressor suction vacuum and discharge or "high side" output pressure. If gauge ports are not installed on the air conditioner compressor unit the technician cannot make this test without cutting the refrigerant lines to install gauge ports (adding to the cost of this diagnosis).

Low air conditioner motor amperage draw

Low amperage draw: unlike a high-amp current draw which indicates that the compressor is danged internally in a way that its piston(s) is(are) tight in the cylinder, a low-amp current draw, if below normal, may confirm internal wear on the compressor parts, and would support the diagnosis that the compressor is worn and inefficient. Where there are no gauge ports to actually measure compressor low side and high side vacuum and pressure, this simple electrical test is a useful first step.

Abnormal air conditioner compressor pressure readings

Refrigerant line pressure readings which are abnormal (probably too low) on the high pressure side (compressor output) or on the low pressure side (compressor input or suction line) can indicate a problem with the compressor's ability to develop normal operating pressure ranges and thus will affect the cooling capacity of the air conditioning system. For more details on air conditioner refrigerant line pressures and how they are examined see COMPRESSOR PRESSURE READINGS

Details about air conditioning compressor functions, how air conditioner compressors work, what goes wrong with air conditioner compressors, and how to measure and diagnose air conditioner compressors are provided at COMPRESSOR CONDENSER.

Cooling Capacity of the Air Conditioning Duct System

Even if a very high BTUH capacity cooling system is installed, if the duct system is defective the ability of the system to deliver cool air to the occupied space can be severely or even totally lost. Duct System Efficiency (in percent) describes the percent of cooled air produced by the A/C equipment which is actually delivered to the occupied space. This number is less than 100% because of air flow restrictions and losses in the duct work. Duct Delivery Effectiveness is the percent of cooling capacity which is delivered through the registers into the occupied space. Registers themselves restrict air flow. See "DUCT SYSTEM DEFECTS" - see links at left.

Cooling Capacity of the Whole Air Conditioning System

So the ability of the entire A/C system to cool a building or rooms in it requires that both the cooling equipment and the duct system be in proper working order.

Details about duct system and air handler diagnosis, including duct defects, air filter defects, and air handler problems are provided at AIR HANDLER UNIT: problems with the air handler, air filters, and the cooling coil itself.

How to diagnose and fix an air conditioning system that is not working

If your air conditioning system won't work, follow our diagnostic guides

Schematic of an air conditioner compressor unit showing inspection points (C) Carson Dunlop

At LOST COOLING CAPACITY, our focus is on the case in which the air conditioning system seems to be "running" but not enough cool air, or no cool air at all is being delivered to the occupied space. Sketch from Carson Dunlop.
At OPERATING DEFECTS we take you through the major air conditioning problem symptoms and how to get the air conditioning system working again.
At CONTROLS & SWITCHES we explain the many electrical switches and controls that control an air conditioner or heat pump system. You'll need to check these if your air conditioner won't start.

See our complete list of air conditioning system diagnostic and repair guide articles just below.

Sketch courtesy of Carson Dunlop

Since the failure of an air conditioner to turn on, loss of air conditioner cooling capacity, reduced air conditioning output temperatures, loss of cool air supply, or even loss of air flow entirely can be due to a variety of problems with one or more components of an air conditioner or air conditioning system, after reviewing the lost air conditioner cooling diagnosis procedures described in this article, be sure to also review the diagnostic procedures at each of the individual air conditioning diagnosis and repair major topics listed just below. To return to our air conditioning and refrigeration home page go to AIR CONDITIONING SYSTEMS.

If your air conditioning system has lost its cooling capacity or won't start select one or more of the diagnostic articles listed below.

...

Technical Reviewers & References

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Daniel Friedman - principal author/editor of the InspectAPedia^® Website
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
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.
Timothy Hemm, Yucala, CA, contributed photographs of electrical wiring and equipment installed in California buildings. Mr. Hemm can be contacted at TimHemm@yahoo.com

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.

CONTROLS & SWITCHES: air conditioner controls and switches - begin here if your A/C won't start. Here's an important tip: most refrigeration problems, in air conditioners, refrigerators, or freezers, are electrical, not mechanical. In air conditioning school, we used to drive out and collect abandoned refrigerators that people were tossing out during our community's spring cleanup week. Taking these appliances back into the shop we found that almost always the problem that had caused the owner to dispose of their air conditioner or freezer was in an electrical connection or electrical control. So it's worth checking out switches and controls on an air conditioner before replacing more costly components.
OPERATING DEFECTS: major air conditioning problem symptoms and how to get the air conditioning system working again,e.g. compressor or fan noises, failure to start, and inadequate cool air volume
LOST COOLING CAPACITY: what to do when not enough cool air comes out of the system
- What to check first if there is no cool air or not enough cool air
- Compressor failure diagnosis: basic checks of the air conditioner compressor
- Ducts & Air Handler diagnosis: basic checks of the indoor air handler (blower), air ducts, and filter systems
COMPRESSOR CONDENSER: problems with air conditioner compressor/condenser units
AIR HANDLER UNIT: problems with the air handler, air filters, and the cooling coil itself
DUCT SYSTEM DEFECTS: problems with the air duct system, air filters, supply registers, return air registers
A/C REFRIGERANT LEAK DETECTION: how to use a TIF5000 to detect air conditioning refrigerant gas leak
A/C DIAGNOSTIC FAQs: air conditioning system diagnostic FAQs: Q&A about air conditioner repair - a detailed air conditioning system diagnostic checklist

A/C COMPONENTS
A/C DATA TAGS
A/C DIAGNOSTIC FAQs
A/C REFRIGERANTS
A/C TYPES, ENERGY SOURCES
AIR CONDITIONER BTU CHART
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER UNIT
  DIRTY A/C BLOWERS
  DAMAGED COOLING COIL
  DIRTY COOLING COIL
  DIRTY COIL CLEANING PROCEDURES
  FROST BUILD-UP
  BLOWER LEAKS, RUST & MOLD
  ADDING A/C: RETROFIT SIZING
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - Air Conditioning "How To" Books
CLEANING & Legionella BACTERIA
COMPRESSOR & CONDENSING COIL
  INSTALLATION ERRORS
  CONDENSING COIL FINS, SUPPORT PADS
  COMPRESSOR NOISES
  HARD STARTING
  TIGHT or SEIZED AC COMPRESSORS
  COMPRESSOR PRESSURE READINGS
  BURNED-OUT COMPRESSOR
  REPLACING A COMPRESSOR
  A/C CAPACITORS
  MOTOR OVERLOAD RESET SWITCH
CONDENSATE HANDLING
CONTROLS & SWITCHES
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
DATA TAGS on AIR CONDITIONERS
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
DEFINITION of Heating & Cooling Terms
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?
FAN AUTO ON Thermostat Switch
HEAT LOSS (or GAIN) in BUILDINGS
HUMIDITY LEVEL TARGET
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LOST COOLING CAPACITY
  What to Check First
  A/C Flow Too Weak
  A/C Filter Problems
  A/C Compressor Problems
  A/C Off - Condensate Pan Switch
  A/C Cooling Coil Icing
  A/C Not Dehumidifying
  A/C Air Duct Problems
  Air Conditioner Won't Start
  Air Conditioner Refrigerant Problems
  Blower Fan No Start / No Stop
  Compressor Diagnosis: Diagnose & Repair
  Cooling Capacity of the Duct System
  Repair Guide Master List
MOTOR OVERLOAD RESET SWITCH
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
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

Thanks to reader and research scientist Cyril Roberts, Barbados, for technical discussion and investigation of air conditioning system dehumidification problems (April 2009).

AIR CONDITIONING & HEAT PUMP SYSTEMS

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