Unit is almost ten years old. Buzzing 24hrs/day. Not related to heating or air operation, just always buzzing.

Unit is almost ten years old. Buzzing 24hrs/day. Not related to heating or air operation, just always buzzing.

Most of the time the buzz is caused by loose plates in the low voltage transformer. Replace transformer and the noise should go away OR sometimes you can shim under the transformer to tighten the plates up a bit to stop the noise.