i7-1370P thermal throttling

[Dell_Notebook]

I have a Dell Precision 3480: 32gb nvidia rtx a500 1tb wd_black sn770m
The issue is: after 30 seconds that the computer start, the fan start and continuously running at a low speed.
I changed the motherboard and the fan kit, but the issue remain.
How can I do?

[n_scott_pearson]

What does this issue with fan control have to do with thermal throttling? Please do a better job of explaining what's going on.

...S