I just started getting a noise from one of my inverters (the left one) that sounds to me like maybe a fan bearing. It's a little higher pitched than the normal fan noise and seems to come and go. I seems to be louder when listening by the lower right side of the inverter. Since this is between the two inverters I guess it could be coming from the lower left side of the other one, but it doesn't sound that way.
I've had computer fans make a similar noise when the bearing was going out or sometimes just from dust in the fan when blowing it out resolved it.
Has anyone else had this issue?
I've had good luck on noisy computer fans before, taking them out, peel off the sticker on the center to expose the motor shaft, then pack in some silicone grease with finger, while turning the fan blade a bit, then clean off the sticker surface really clean and dry and putting the sticker back on (or a piece of duct tape if the sticker no good anymore), to keep dust from getting in..
I've done this in a bind (it has worked for me several times to quiet down noisy bearings on cooling fans), you can also take a picture of the sticker of the fan and just go search for that model and p/n or get the specs off it and order another of the same or similar, as long as it's right like diameter of mounting flange, RPM, volts/amps, 2-wire, 3-wire, 4-wire, etc...
But usually they have a p/n and brand, and I can easily locate the exact same fan somewhere.
If you were not sure whether the noise is fan noise, you could bench test them one at a time and see if they all sound the same. Also pay attention to when the fans should be off, or at low speed and see if the noise you hear is quieter, or fan rpm change corresponds to the noise you are hearing. Perhaps the high pitch noise is a failing mosfet or transistor (corresponding to the switching frequency)...
