Diagnose humming air conditioner or heat pump noises or sounds at air conditioners or heat pumps or at heating systems & in HVAC duct systems or air handlers.

Air conditioner or heat pump noise diagnosis & cure: this air conditioning repair article series 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.

Humming Noise from A/C System: compressors or other electric motors in trouble

Here we give a catalog or index to our more-detailed diagnostic and repair articles for various causes of humming noises that may come from an air conditioner, heat pump, indoor or outdoor units or from a heating boiler or furnace.

HVAC Air Handler OR Compressor/Condenser Humming Noise 10-point Checklist

1. Normal electric motor humming:
   
   nearly every electric motor makes a soft, continuous humming sound when running; this doesn't indicate a failure.
   
   When you swap in a new electric motor to an air handler or for a condenser fan, differences in manufacturer's motor quality may give you a motor that hums a bit louder.
2. Humming at a low voltage transformer:
   
   where a low-voltage transformer is nearby, such as a 24VAC transformer operating thermostats or other device, check the transformer itself.
   
   See also LOW VOLTAGE TRANSFORMER, TRANSVERTER DIAGNOSIS
   
3. Humming Hard-starting motor:
   
   check for a bad start capacitor; ultimately check for a failing electric motor, bad bearing, bad winding, or failing compressor motor. Check current draw during start-up
4. Humming contactor relay or switch:
   
   some failing contactors or relays hum rather than buzz
5. Humming vibration noises:
   
   check for loose motor mounts, out of balance fan in the air handler or at the compressor, worn fan bearings; also check for transmitted vibration noises carried by metal part like the refrigeration tubing
6. Humming air handler noises:
   
   after checking the blower fan motor and fan assembly for lost fan weights or a bent, damaged squirrel-cage fan and for bad fan bearings, check for icing or freezing starting a the cooling coil
7. Humming oil burner noises:
   
   are explained in detail at
   
   at OIL BURNER HUMMING NOISE
   
   
8. Other Electric Motor Failures
   
   See ELECTRIC MOTOR HUMMING
   
   And because people's interpretation and naming of mechanical system noises varies,
9. Similar noises some people mayu call "humming:
   
   Also see HVAC NOISE-2 CHATTER CHIRP CLANK CLICK FAN GRIND GROAN - chattering, clanks, clicks, clunks, cyclical, fan, groans, growls, honking
   
   Also see BUZZING NOISE DIAGNOSIS - extensive list; check first for most-dangerous: arcing buzzing contactors, relays, or any other arcing electrical component;

Additional diagnostic suggestions and detailed HVAC humming noise diagnostics are given in the Q&A found below.

The following HVAC noise descriptions are in this same noise category.

Other Noises whose Cause Can also Produce Humming

• HVAC NOISE-3 HISS HOWL HUFF HUM - hiss, howl, huff, hum, groan, woo wuwuwu wuff or humming noises
  • HISSING SOUNDS, HVAC from A/C or heat pump system - separate article
  • HOWLING HVAC sounds from air conditioners, air handlers, blower fans, heat pumps, furnaces, duct systems & their motors
  • HUFFING sounds from A/C or heat pump system, diagnosis
  • HUMMING NOISES from HVAC SYSTEMS sounds from A/C or Heat Pump system condenser or air handler

Photo above: a lost balancing weight on a squirrel-cage blower fan can cause vibration that may be described as "humming".

Fan counterweights are detailed at BLOWER FAN ASSEMBLY CLEANING

...

Continue reading at HVAC NOISE-3 HISS HOWL HUFF HUM - loud start up noises, popping, rattling, rumbling, running water or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see HUMMING NOISES from HVAC SYSTEMS FAQs - diagnostic and repair questions & answers posted originally at this article

Or see these

Recommended Articles

• BLOWER FAN ASSEMBLY CLEANING
• ELECTRIC MOTOR HUMMING
• HUMMING NOISES in BUILDINGS - complete list of sources of humming sounds at or in buildings
• HVAC NOISE-1 BANG BUZZ VIBRATE - banging, bearings, buzzing, thumping
• HVAC NOISE-2 CHATTER CHIRP CLANK FAN GROAN - chatter, chirp, clank, clunk, cyclical sounds, fan noise, groan, growl, gurgle
• HVAC NOISE-3 HISS HOWL HUFF HUM - hiss, howl, huff, hum, groan, woo wuu wuff
• HVAC NOISE-4 POP, RATTLE, ROAR, RUMBLE - loud start, popping, rattling, roaring, rumbling, running water
• HVAC NOISE-5 SCREAM SING TRUMPET WHINE WUWU - scream, sing, squeal, trumpet, water sounds, whine, whoosh, whistle, wuwuwu, or silence
• LOW VOLTAGE TRANSFORMER, TRANSVERTER DIAGNOSIS
• NOISES, HVAC SYSTEM DIAGNOSIS - home
• OIL BURNER HUMMING NOISE

Suggested citation for this web page

HUMMING NOISES from HVAC SYSTEMS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE I NDEX to BUILDING NOISE DIAGNOSIS

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In addition to any citations in the article above, a full list is available on request.

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