I just noticed that a relays (SPST) that I am using for my project have constant but really quiet buzzing noise. The buzzing noise stops when relay is active.

Is this normal?

  • \$\begingroup\$ Are you using it to switch an AC source? 60Hz perhaps? Also, is active open or closed? \$\endgroup\$
    – Samuel
    Commented Oct 4, 2013 at 21:34
  • \$\begingroup\$ The relay is supposed to be for cars and is rated at 12VDC at 60A max. \$\endgroup\$
    – jM2.me
    Commented Oct 4, 2013 at 21:36
  • \$\begingroup\$ Ok. And active is open or closed? \$\endgroup\$
    – Samuel
    Commented Oct 4, 2013 at 21:42
  • \$\begingroup\$ If you unsoldered it or disconnected it from the circuit do you think it would still buzz despite your assertion (and the implied opposite) that it stops buzzing when active? \$\endgroup\$
    – Andy aka
    Commented Oct 4, 2013 at 21:44
  • 1
    \$\begingroup\$ A relay can buzz if there is insufficient voltage/current on the line. Not enough to turn the relay on, but enough for it to try. Check the line for stray voltage and current. \$\endgroup\$
    – Passerby
    Commented Oct 4, 2013 at 23:44

1 Answer 1


It's not nominal but not uncommon, so it'll depend on your definition of normal.

Most likely you are not providing enough power to hold the relay in whatever state it's in when powered. If it's close to the correct value, it'll operate, but will rattle or buzz.


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