DELL Precision M4500 FAN ALWAYS ON 2600RPM

Hello. I have problem with my DELL PRECISION M4500.
Intel I7 Q820M  NVIDIA FX880m

Look screenshot. My temperatures. Fan Always on (2600RPM). FAN is little noisy (my laptop worked a lot of hours (13.000 hours) Should I replace my old fan with new ?



Two months ago I changed thermal paste (Now is CERAMIQUE2) and thermopad's (Laird 5W)

What temperature I need to disable fan ?  

FN+SHIFT+1532 (engineering mode) work, but I can't go to thermal control menu (FN+R). It didin't work on M4500. I think other key Combination

Thanks for any help, and regard's