How to identify the 3 thermals sensor connectors from the mac mini motherboard?
I suspect that you have found the answer via other means, but I'll answer it for the next person that finds their way here.

I was looking for a way to repair the connector on the motherboard when I found this question unanswered.  I'll continue my search after answering.

So, after much double checking:


One of them is for the DVD.


This is connector J5550. From your perspective, the left one.

One of them is for primary HDD near the connect.


This is connector J5560. From your perspective, the right one.

One of them for the primary HDD on the side (glued).


This is connector J5520. From your perspective, middle one



PS: I would recommend including your Mini model in the future.