AND here I was logging back on to ask you if you were referring to the Viscous
Fan Clutch on the Mechanically driven Fan(Between the Radiator and the Engine).
You can sorta test the Viscous Clutch by spinning it by hand...BUT you have to
do it with a warm engine (80 degrees centigrade or higher)...that, you have just Shut Off. (And I mean within 5 sec.)
Pick any electric fan you can find...If you (or anyone else on Planet Earth)can
determine the Wear Length [percentage of the original brush length remaining]
by spinning the fan blades,and sensing by some as yet invented process,the
friction co-efficient of the remaining brushes as compared to the friction
co-efficient of new brushes...You have created a new Mechanical cottage
Industry and will retire a rich person.
The rest of us fumbling DIYers have to remove the brushes and eyeball them
with a measuring device to determine usable life left in them.(Heck,it's so
much hassle,ONCE they are out you just replace them as a matter of course.)
I am not even sure the difference between worn and new brushes could be
measured electrically [Ohm meter or a DC amperage meter] (with the motor still intact)
But you've got me thinking about that possibility...NAAH,the resistance for
new and worn brushes should be the same...Unless worn brushes draw more
current than new ones?
member TOMJ posted this excellent aux fan bearing R+R (its for a single fan
but would apply to the dual aux fans also).If you get this far the brushes
would be a piece of cake.
Bosch Aux Fan - New Bearing/Rebuilt - 123 Body
Jim Forgione has The Best web page for cooling system "Fixes",I would
especially recommend #s 17,18 and 20 on his page for you!
http://pages.prodigy.net/jforgione/MB_S500.html
I've relayed your inquiry to stevebfl (an expert),who will hopefully reply
in the A.M.
It is my personal belief that man was allowed to create automobiles,primarily
as a transport device for "Angel's Breath". (Air Conditioning)