Fan clutch questions

Warning in advance that this is a cross post...

I'm about to replace the fan clutch on my 165K mile '94 XJ. I'm going to use a thermostatic model ($50 at C.A.P.), but my question is: how do I know what temperature the clutch will engage at? And, is the engagement temperature adjustable with the little bi-mettalic coil on the front?

Thanks!

Andy

Make sure it is no longer than the old one or you will hit the radiator. As for adjsutment, don't think there is any on that type.