Skip to content
forebot.
Sign inBook a demo

Unusual noise or vibration from the equipment.

A trained tech should do the checks, and refrigerant work goes to a technician with the required refrigerant credential.

Customers put it like this

  • The outdoor unit is buzzing
  • There's knocking from the compressor
  • It squeals when the blower starts
  • The contactor keeps clicking
Prepare this job in ForeBotFind another guide

Stop first if

  • A compressor terminal or cover is damaged, or oily spray shows at itKeep clear. Shut off at the disconnect only if it can be done without risk. Call a licensed tech.
01

Ask on the call

6

Homeowner? These are the questions a good technician will ask you. Having the answers ready makes the first visit count.

  1. Is it a buzz, click, knock, squeal or rattle?
  2. Does it happen at start, while running, at shutdown or during defrost?
  3. Where is it loudest?
  4. Do the lights dim when it starts?
  5. Was any work done recently?
  6. Can you send a short clip of the sound?
02

Bring

5
  • Electrical meter
  • Clamp-on current meter
  • Digital manometer
  • Phone for sound recording
  • Flashlight
03

Check on site

6
  1. Log each sound and the moment it happens, in each mode.
  2. Note normal events first, such as the defrost shift or the valve whoosh.
  3. For clicking or buzzing, read coil and line voltage together through a loaded start.
  4. For squeal, check belt and alignment with power locked out.
  5. For pulsing air, read static pressure and watch for surge.
  6. For knocking or a sweating shell, a refrigerant-credentialed tech reads compressor suction superheat.
04

Keep on the record

5
  • Sound clip
  • Timing notes by mode
  • Voltage readings
  • Belt condition photo
  • Static pressure readings

General guidance for a qualified person, not a finding about any home. The person on site decides.