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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
HVAC blower fan testing & diagnosis guide: this article discusses how to inspect and test a heating or air conditioning indoor air handler blower fan that is not working. We also discuss convector unit fans and we suggest diagnostic steps for squirrel cage blower fan squeaks and noises.
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How do I fix my indoor air conditioning or furnace blower fan: the air conditioning (or heat pump or furnace) blower fan just won't run
For completeness we have listed some blower fan diagnostic steps that you have already tried, as well as additional things to check. The blower assembly is the green component in this illustration from Carson Dunlop Associates The Illustrated Home.
Thanks to reader Randy Shaffer for suggesting this topic.
Frequently Asked Questions (FAQs) about heating or cooling system air handler blower fans
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Squeaky Squirrel Cage Blower Fan Noises: Diagnosis, Cure
Question: What do I do about a squeaking, squalling squirrel cage? It doesn't do it every time the A/C comes on but more frequently than not. Not alot of room to see in there. WD-40? Any suggestions? - Erma
Reply: Check for Loose Blower Fan Parts, Lubricate with the proper oil or grease
The squirrel cage fan to which Erma refers is found inside the indoor air handler unit. This fan moves building air through the duct system and across heating and/or cooling elements to condition the air as it is then supplied to the building through supply ducts and registers. In an air conditioning system this is the dark blue fan shown in the right side of our sketch above. For combined heating/cooling systems the same fan assembly can blow heated air into the building and an additional FAN LIMIT SWITCH will be found inside the furnace cabinet.
More about HVAC blower fans including squirrel cage fans is in this article, above beginning at BLOWER FAN OPERATION & TESTING but to start addressing a squeaky blower fan, note that your fan may be repairable by tightening one or more allen screws that secure the fan cage assembly (or the bearings that carry the fan) to its housing through which passes the fan motor drive shaft.
Some HVAC blower fan assemblies use a grease fitting not oil. In that case your service tech may need to re-pack the bearing with grease; often on older units there is a grease cap over the fitting that, if tightened, forces more grease into the bearing, so if you see one of those, try first giving the cap a turn. .
Air Handler Blower fan motor runs backwards
The cause of a backwards-running fan (and some other electric motors) could be a bad start-run capacitor (see CAPACITORS for HARD STARTING MOTORS) or a bad control board. More rare, incorrect wiring or internal damage to the fan motor windings.
Details about diagnosing and fixing a condenser fan that was running backwards are discussed in our companion article on compressor/condenser units, at Questions & Answers about compressor/condenser unit fans. Also see BLOWER FAN OPERATION & TESTING
My Heating Furnace Blower Fan Won't Start & Furnace Burner Shuts Off - what do I do?
Question: the furnace burners go on but the blower fan does not and then the flame shuts off what's wrong?
I have a american standard furnace freedom 80 the burners go on but the blower fan does not and then the flame shuts off what's wrong? - Robert.
Reply: the fan limit switch is turning off your heating furnace burner because the fan is not starting. Diagnose and fix the blower problem.
Robert, if the furnace blower fan will not start, the limit switch on your furnace will turn off the burner in order to avoid overheating and damaging the heat exchanger. You'll need to inspect and fix the blower fan problem. If your furnace blower uses a drive belt to connect the fan to the driving motor check that the belt is in place and not slipping. Other blower fans use a direct drive motor whose shaft spins the fan assembly. IN either case check that the motor is starting;
Question: adjusting blower fan speed in an air conditioner, heat pump, or furnace system
How do you adjust the blower gas furnace to speed it up a little bit? The reason is that I'm adding 300 sq feet. Also how do you open the cover of the cooling coil? - Hoa, 8/16/11
Reply: How to increase the heat output from a gas fired furnace or cool air output from an air conditioner
Thank you for replying! I live in California and my concern is about the cooling system. The house I bought is 1-story, about 1500 sq ft. (originally, this house was 1100 sq ft but an extra room was added to the back of the house). What should I do to connect the air ducts of this new room to the original-sized air ducts in the rest of the house?
Hoa the duct question needs to be answered by an on-site HVAC installer with some expertise and experience - I simply can't know enough from simple text Q&A to give a solid answer to sizing, routing, placement of registers, etc.
Questions & answers or comments about heating or cooling system air handler blower fans .
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
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 & HEAT PUMP SYSTEMS.
If your air conditioning or heat pump system has lost its cooling capacity or won't start select one or more of the diagnostic articles listed below.