1. Check the Room Thermostat Temperature Setting: Set the thermostat to at least 5 degrees below room temperature. Our elderly mom has no patience with switches and controls. She regularly calls her air conditioning service company with a service request, sometimes late at night, because she has simply failed to set the temperature on the thermostat lower Get A/C Price Estimates Free Cost Estimates from Local Air Conditioning Contractors. www.homeblue.com/air-conditioning
LONG-ON CYCLING AC COMPRESSOR MOTOR OVERLOAD RESET SWITCH NOISES, COMPRESSOR CONDENSER Pressure Controls & Safety Switches PRESSURE READINGS, COMPRESSOR REPLACING A COMPRESSOR SHORT CYCLING AC COMPRESSOR TIGHT or SEIZED AC COMPRESSORS CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS CONDENSING COIL
COOL OFF HEAT Thermostat Switch COOLING CAPACITY, RATED COOLING COIL or EVAPORATOR COIL DAMAGED COOLING COIL
DIRTY COOLING COIL
DIRTY COIL CLEANING PROCEDURES FROST BUILD-UP on AIR CONDITIONER COILS INCREASING RETURN AIR
DATA TAGS on AIR CONDITIONERS DEFINITION of Heating & Cooling Terms DEHUMIDIFICATION PROBLEMS DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP DIAGNOSE & FIX HEATING PROBLEMS-BOILER DIAGNOSE & FIX HEATING PROBLEMS-FURNACE DUCT SYSTEM & DUCT DEFECTS
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper DUCT INSULATION for SOUNDPROOFING DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe DUST CONTAMINATION FROM HVAC? EDUCATION, HVAC SCHOOLS ELECTRIC MOTOR DIAGNOSTIC GUIDE ELECTRIC MOTOR OVERLOAD RESET SWITCH ELECTRICAL POWER SWITCH FOR HEAT ENERGY SAVINGS in buildings
EVAPORATOR COIL or COOLING COIL EVAPORATIVE COOLING SYSTEMS EXPANSION VALVES, REFRIGERANT FAN, AIR HANDLER BLOWER UNIT FAN AUTO ON Thermostat Switch FAN, COMPRESSOR/CONDENSER UNIT FAN CONVECTOR HEATERS - HYDRONIC COILS FAN LIMIT SWITCH
FAN NOISES
FURNACES WARM AIR HEATING SYSTEMS GAS EXPOSURE EFFECTS, TOXIC GAS DETECTION & MEASUREMENT GAUGE, REFRIGERATION PRESSURE TEST
than the room temperature. Don't drive your A/C like our mother. 2. Check that the Room Thermostat is set to "Cool" not "Off" or
"Heat". If the thermostat is not set to "cool" it is simply turning off your A/C. 3. Check that electricity is on for the equipment. Check all switches
and controls, including service switches, including outside by the compressor, inside at the air handler, and fuses or circuit breakers in the electrical panel. For example, condensate spilling into an overflow pan that uses a sensor switch can be enough to shut down your air conditioner. There are several switches and controls, both manual and automatic that can leave an air conditioner or heat pump turned "off" such as a blower compartment door interlock safety switch, an electric motor overload or overheat switches, and a condensate tray spillage detector switch.
Watch out: See A/C - HEAT PUMP CONTROLS & SWITCHES to be sure you have found and checked every manual or automatic electrical switch on the system. A bad or failed starter capacitor could also be leaving your system shut down, failing to start a blower, fan, or compressor motor. Some hard-to-find switches could be keeping your air conditioner from starting, such as a Float Switch on Condensate Tray or a blower MOTOR OVERLOAD RESET SWITCH
If the air conditioning system is still not working, or if the A/C system is running but cool air is not coming out of the supply registers you probably need to call a service technician, but below are some things to check further yourself.
If At Least Some of the Air Conditioner or Heat Pump Equipment is Running but
Cool Air is Not Being Delivered - 5 Quick Diagnostic Air Conditioning / Heat Pump
System Checks to Get the Air Conditioner Running Again
The basic air conditioning diagnostic checks just below are followed by more detailed investigation of why the air conditioner is not working. But unless you already have a good idea of what's not working, start with these five steps. If the air conditioning system is still not working, or if the A/C system is running but cool air is not coming out of the supply registers you probably need to call a service technician, but here are some things to check further yourself. Just after these checks we discuss what to do if the air conditioner is running but air flow is too weak (A/C Flow Too Weak) or too warm.
Step 1: Check the Outside Air Conditioning /Heat Pump Compressor-Condenser
unit
Is the outdoor compressor-fan unit (COMPRESSOR & CONDENSING COIL) running?
If not, be sure that the outdoor compressor/condenser unit service switch and the air conditioner indoor power switch, fuse, or circuit breaker are all in the "on" position.
Check the outside compressor condensing coil for damage or blockage.
HEAT LOSS (or GAIN) in buildings HEAT LOSS (or GAIN) INDICATORS HEAT LOSS R U & K VALUE CALCULATION HEAT PUMPS
HEATING SMALL LOADS
HOUSEWRAP AIR & VAPOR BARRIERS HUMIDITY LEVEL TARGET
INDOOR AIR QUALITY IMPROVEMENT GUIDE INSPECTION CHECKLIST - OUTDOOR UNIT INSPECTION LIMITATIONS, A/C SYSTEMS LEED GREEN BUILDING CERTIFICATION
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
LOW VOLTAGE TRANSFORMER TEST MANUALS & PARTS GUIDES - HVAC MOTOR OVERLOAD RESET SWITCH MOLD in AIR HANDLERS & DUCT WORK ODORS in AIR HANDLERS & DUCT WORK OPERATING COST
OPERATING DEFECTS OPERATING TEMPERATURES Air Conditioning System Temperatures Instruments Used to Measure A/C Temperatures Procedures for Making Temperature Measurements PORTABLE ROOM AIR CONDITIONERS
PRESSURE READINGS, REFRIGERANT
REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS & PIPING
GAUGE, REFRIGERATION PRESSURE TEST REFRIGERANT CHARGING PROCEDURE REFRIGERANT DRIERS & FILTERS REFRIGERANT LEAK DETECTION REFRIGERANT LEAK REPAIR
REFRIGERANT METERING DEVICES TEVs
A blocked condensing coil can cause the compressor to overheat, stop running, or become noisy and work poorly. A/C Compressor Problems
If you cannot find your air conditioner controls and switches see A/C - HEAT PUMP CONTROLS & SWITCHES - list of controls and switches found on air conditioners and heat pumps
Also check the compressor/condenser outdoor fan and fan motor
Condensing unit fan diagnostics: at FAN, COMPRESSOR/CONDENSER UNIT we explain the diagnosis of problems with the compressor/condenser fan and fan motor.
At BURNED-OUT COMPRESSOR we explain that if the condensing unit fan is not working the compressor itself may shut down or even be ruined by overpressure or over temperature. Also see NOISES, COMPRESSOR CONDENSER where some noise problems are traced to the cooling fan .
Step 2: Check the Air Conditioning /Heat Pump Indoor Air Handler
Is the indoor blower unit running? If not be sure that the electrical power switch at your furnace or air conditioner air- handler is in the "on" position. Typically the air handler or blower unit is indoors inside the basement, crawl area, or attic.
Sometimes there is more than one switch, such as one right at the unit and another at the entry to the room where the equipment is located, or even upstairs on a higher floor if your air handler is in a basement or crawl space.
Make sure that the blower compartment cover or door is properly closed or an interlock switch may be keeping the system "off".
Also remember to check for a dirty, blocked COOLING COIL or EVAPORATOR COIL. A coil blocked by ice or dirt will not produce cool air. A/C Cooling Coil Icing.
Step 3: Check the Air Conditioning /Heat Pump Air Filter(s)
If your air conditioning equipment is running but little or no cool air is coming out of the supply registers, check that your air filter(s) have not become blocked with dirt and debris.
REFRIGERANT METERING CAPILLARY TUBES REFRIGERANT PIPING & DISTANCES REFRIGERANT PIPING INSULATION REFRIGERANT PRESSURE READINGS REFRIGERANT SIGHT GLASS
RETROFIT SIZING for A/C or HEAT PUMPS SEER RATINGS & OTHER DEFINITIONS SOLAR ENERGY SYSTEMS
SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS SWAMP COOLERS
SYSTEM OPERATION
THERMOSTATS, HEATING / COOLING THERMOSTATIC EXPANSION VALVES WATER COOLED AIR CONDITIONERS WINDOW / WALL AIR CONDITIONERS WINDOW / WALL A/C SUPPORTS More Information
Usually the air filter is right at the air handler or blower unit, or your air filter may be installed behind a grille covering a central warm-air return that sends air back to the air handler. See A/C Filter Problems
Step 4: Check the Air Conditioning /Heat Pump system duct work & air supply
registers
In ceilings, walls, or floors, where cool air is supposed to be delivered to various rooms in the building, be sure that the register is in the "open" position (you will be able to see through it into the ductwork) and be sure you haven't blocked the supply registers with a carpet or furniture.
Look for a duct damper or register that has been closed; look for a flex-duct section that has become disconnected, bent, or crimped or squashed. Remember that a duct may have become disconnected in an attic or crawl space. Look for an air filter that has come loose and blown into the ductwork, clogging it.
At left you can see a ceiling air supply register that has leak stains around its opening - further investigation for a condensate leak or roof leak is needed.
Step 5: Check the Air Conditioning /Heat Pump indoor air handler blower fan
assembly
If the indoor air handler blower fan itself won't start, see BLOWER FAN OPERATION & TESTING. Check for lost power, a fan motor that wont' start or has tripped a motor reset button or needs a start / run capacitor. Check for a blower fan that is loose on the motor drive shaft or for a broken or lost blower fan drive belt on pulley-driven blower systems.