A1347 2010-2012 common issues
Shorted Tantalum Polymer Capacitors
Tantalum Polymer Capacitors on the 5V rails can become short. These capacitors are for USB 5v line. if they become short then the mac mini will not turn on.
remember capacitors polarity. check the green circled caps for short.
the value of the cap is 150UF, 6.3v, Case B2. https://uk.farnell.com/panasonic/6tpg150mzg/cap-150uf-6-3v-tant-polymer/dp/2982731
Quarter Fan spin.
No water damage.
In most cases a quarter fan spin on in this year is a corrupted EFI chip. You will need to dump the proper bios of the year and model into the Mac Mini. De-Soldering the original Bios chip and reprogramming it will help resolve the issue. (be sure to follow the guide on cleaning the ME region)