DELL 1815DN printer - variable speed fan "whine" noise from right side of unit when idle

Installing a Dell 1815DN printer that was used briefly in 2007 then stored indoors with no use at all until (September 2020). Other than a bit of surface dust, it's basically as it was then. I was the administrator for the printer back then and I will be now.The printer powered up (a bit of "dust" smell for the first couple of minutes, but this dissipated), and I was able to reset and then establish printer and network settings. I completed the "maintenance" menu command (I believe a drum clean operation) without difficulty.The printer is running successfully so far and print quality is normal with no sign of toner problems. The system data list reflects 3.3K pages total and 83% toner remaining (I don't recall if the toner was ever changed from new). Firmware is 1.03.03.08 and Engine is 1.00.41.

Here is the problem - the printer is emitting a quite noticeable whining sound from the right side (near what looks like a cooling air vent.) The whine only seems to happen when the printer is idle (not sleeping or powered down - just powered up and awaiting a print job). It sounds like a speed controlled cooling fan (maybe around 500 Hz pitch most of the time, but moves up or down in pitch or stops entirely when the printer is called on to print a page). I don't remember the noise when I was sharing space with it in 2007 (it was in a small, nondescript office).

What is the cause of this sound? Should I be concerned for (very occasional) use (it won't be powered on continuously, just when occasionally used)? If it is a concern, where can I find documentation that would tell me how to gain access to the area where the (fan?) is located?

Thanks very much for any advice!