Thanks for the details!
Ok, so in your case the fans are working properly, their speed ramps up as the temperature increases, which is normal. Tbh, at first glance, your card seems to be functioning normally, as it should, at least as far as its fan controller is concerned. At least we have that out of the way.
Now could you please run something else, like a synthetic benchmark (Unigine Heaven 4 will do the job nicely) so that we may know what’s the max temp and the gpu fan speed under full load in something other than D4 for reference?