I just had the capacitor in my furnace changed, but it is now making a whistling noise that it did not make before the repair. What is wrong with my furnace?


It's possible the unit is running better therefore perhaps revealing small holes in your ducting. If these gaps were plugged with dust, you wouldn't hear it or perhaps the blower was working too hard thus not moving as much air so now that it is, it's revealed that you have leaky ductwork. Pinpointing the whistle and simply putting a piece of tape over it should fix the issue. That's my guess from here.

Updated on February 22, 2018

Original Article:

How to Quiet a Noisy Furnace
By Dan Robbins