Prime95? ouch! No wonder you are not seeing any variations in temps since the program itself isn't working properly. That's a rather out dated one too at this point.
The sensors are built right into a board where the only thing you can do is simply use a can of air cleaner to clean the case out every so often along with the fans. For a program that will read actual better over many PC Wizard 2008 has been used to read cpu, board, and drive temps here with a 6000+ X2 in use.
A well cooled case with only light activity and no large demands on cpu time will see temps only vary slightly over a period of time. With obsolutely no changes seen the program is the problem where you need a replacement or look over the hardware monitor seen on most boards in the bios itself.