Pulling the fithwheel in 80 deg temps,70mph, hills cause downshift and the temp climbs to 221 and set edge alarm off, as soon as the fans kick in its fine 1/2 mile and temp drops back to 210 +/-, next hill fan is on prior and it fine next hill same as the first and so on, if I set'er at 75 its not as often- more air I assume.

It's not adjustable as far as I know. I know it scares the crap out of you the first time you hear it. After that, it's just annoying. But it does it's job very well.

I read there is a TSB for a different fan cluth for overheating on trucks used for plowing snow. I am not sure if this applies to gassers or the 6.6. I believe it brings the fan in at a lower temp.