Fan trouble - 89 200QW

[Shaun Folkerts <fiatlancia@earthlink.net>]

Happy Holidays to the list, and thanks for all of your help with the
Audi.

I will be departing on a long trip in a few days, and tomorrow is my
last chance to get any work done on the car. There is one annoying
(potentially dangerous) problem I need to fix by the time I depart.
Please, someone, suggest a possible cause and/or remedy...

My coolant fan has never come on after (hot) engine shutoff. Boring,
right?

Now for the interesting part. If I shut off the engine _before_ allowing
the car to warm up, the fan will come on and not turn off - EVER (until
I restart it or the battery dies!). Seems backwards, no? After shutting
off the engine, the fan runs and runs if engine is cold, but won't come
on when engine is hot?!?!

I replaced the multifunction switch/sensor. I have found there are two
wires with red (?) plugs connected to a sensor just above the mfs that
kill the fan when I pull one wire (or both) from the sensor. I tried
reversing them with no change.

Is this sensor the problem (i.e. bad)? Do I have a bad ground somewhere?
Is it something else I am unaware of?

Timely help from the listsperts would really be appreiciated on this
one.

TIA,
Shaun Folkerts