[dwcsr]

I'm not getting into the semantics of cooling water or engines the end result is cooling the engine parts.

The most accurate temp readings are in the head or manifold where the heat is generated. The notion of your engine being to hot for a switch in the head doesn't make sense unless I miss read it. Water temps vary greatly through out the motor and radiator as much a 100 degrees. The Tstat keeps your engine at a minimum temp and the fan stat turns your fan on at a minimum temp to help regulate that temp. If you don't want the switch in the motor then you need an adjustable with a probe in the radiator so you can calibrate it to the gauge.

If you want your fan on at 185 then put a 185 fan switch in the head and use a 170 Tstat and your done. Don't over think this your not launching a shuttle.

All fan switches are +/- 5 degrees for the expensive ones and +/- 8 degrees for the cheap $15 ones. That means they could come on at 185 one time and maybe 193 the next and 178 the next. So don't cheap out the the switch