Steve said,
"It turns out that the temp sensor leaks..and coolant went
right into the plug and shorted it out...causing the fan to
be on high at all times..."       Rather than simply replacing that defective
high temperature thermostatic switch with an identical replacement, consider
this:

I'm not looking for a war here, but It's long been MY opinion (you may not
share this opinion, and if you don't, that's fine) that the heat values of the
high temp and low temp radiator mounted thermostats which control the high
speed and low speed windings of my diesel Westy's radiator fan, were poorly
selected by VW engineering.  I suggest replacing the low-temp low-speed
controlling thermostatic switch with a new one having a lower actuation
temperature.  Then, replace your high temp thermostatic switch with the old
low temp thermostatic switch.  To preserve easy reversibiliy, don't throw away
that old high temp thermostatic switch until you've satisfied yourself that
this is a better match between engine heat and automatic fan cooling.

The effect I experienced was that both the low speed winding came on earlier
and high speed fan circuit came on automatically for the first time ever.
Before I made this modification to my fan controlling circuits, even in the
worst of Florida's summer heat, I NEVER heard the fan come on at high speed
without using my manual over ride switch which I had felt compelled to
install.  Now that manual switch isn't needed.  The heat gauge used to
occasionally indicate that I was running very hot.  After these simple
changes, the heat gauge never showed alarmingly high temperatures again.  I'd
make that decision again in a heart beat.

Bentley shows the heat value ratings of these thermostatic switches.  FLAPS
can get equivalents with different heat ranges.  Just my opinion, but it
worked for me.
John