Drobo 5N fan immediately starts when plugged in, then turns off when drobo turned on

The full story is that I replaced its fan, and took the connector of the old fan and wired / soldered it onto the new one replacing its connector. That’s pretty much all I did except, of course, disassembling it, but was careful not to damage anything else. Any ideas on what could have gone wrong? The device was working perfectly, I just really hated its noisy fan. I replaced it with this one: https://www.amazon.de/gp/product/B00KF7R49S/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

The fan only runs when needed. If everything else is working as usual I wouldn’t worry about it.

I might have not been very clear, and I might just be me, but it’s hard for me to believe that the fan would be needed when the device is off, hasn’t run for days, and would suddenly NOT be needed as soon as I turn the device on? That somehow doesn’t sound right to me…