Noisy inverter....anyone?

Our inverter just started getting "noisy"..anyone have a clue what's happening?  We have a 2012 2910 on a ford 450 chassis

The first thing I would think of is the inverter fan.  Usually these are muffin fans, you can get them at a reasonable price at an electronic store.  If you go to an RV shop they are generally more expensive.

If you hear like a high pitched whine, a constant squeak or shrill sound then I would suspect a bearing in the fan. 

I took off the bottom panel to expose the fan and it seemed to be operating correctly. It ( inverter) seems to go from a low pitched sound and intensify and get louder

So does mine. But that doesn't seem to be a change from the day we bought it.

Only two things that can make an Inverter noisy.  One is mechanical which would be the fan.  The other is the electronics of inverting DC to AC and you would need to be sensitive to the 60 cycle frequency which for the most part is not detectable by the human ear.  Sometimes there are physical parts of the  inverter and other devices that are in the close proximity that will pick up the 60 cycle frequency and resonate mechanically at that rate.  I have seen that happen in aviation.
     Bob

Odds are it's the fan which is normal with PC's.  There's an old string on this forum on fan noise and what some have done from turning the breaker off to installing a switch to turn it off at night