Static-like noise from cabin fan

We recently noticed a continuous noise coming from behind the glove box whenever the cabin air fan was on. It sounds like radio static, but does not come from the audio speaker, and varies from hissing to scraping sounds that Do Not Vary in pitch or intensity with how fast the fan is running, but disappear as soon as the fan is powered off. Pulling out the air filter did not affect the noise in any way, and the air flow from the fan itself is normal, as is the A/C function. My initial thought was that there is a bad bearing in the fan, or an entrapped leaf or other debris, but I would have expected differences in pitch with differences in fan speed. My plan for today is to unplug, but not remove the fan itself and see if there is sound when the fan switch is in the ON position, and failing that, to pull the fan.

Is there anything else in that region of the car that moves or would have air flow to generate a noise, or perhaps act as an electrically driven speaker?

My marriage may depend on a prompt fix!!!

Thanks,
Rob McC

 

The denouement: I pulled apart the cabin fan housing, pulled out the fan and removed the impeller drum and then ran the fan isolated on the floor of the passenger side. My noise came from the fan, apparently from corrosion/debris along the shaft or bearings, or perhaps from brushes that were starting to wear down too much. I could not remove the motor from its housing, so no further diagnostics were possible. A few squirts of WD-40 may have reduced the noise a bit, and all the in-and-out of restoring the fan to its place pending replacement has made the noise more intermittent and variable. While on the floor, changing the speed still did not alter the sound characteristics.... go figure???? Live and learn.....

Rob

 

A new one is on its way from Amazon. $45 includes shipping.
Rob