S4 Electric Radiator Fan Problems

[Mastovsky David <mastovsky.d@mellon.com>]

I'm hoping that someone out here in quattro land can shed some light on
my problem.
I have a 93 S4 with about 40k miles that has developed a problem with
the electric radiator fan.
I believe that when the car is hot and is shut down, this fan is
supposed to come on for a certain period of time.  What has been
happening lately is that the fan will come on and not shut off(until of
course the battery is dead).  The fan will stop when one of the relays
(I forget which one it is) is pulled and start-up again as soon as the
relay is replaced.  I have tried a spare relay that I had, but the same
occurred. (Both relays are good BTW)  I also thought that it might be
the temp. sensor on the radiator so I unplugged the connector; no
success here either.  Looking at the fuse panel I noticed a fuse(number
18 I believe) for something like a Radiator Fan Time Delay (5 cylinder
only). Is this the culprit?
But wait there's more...   Sometimes when I remove the relay and replace
with the same relay the fan will not come back on.

Can anyone help me?!?!?  Are there any other temp. sensors that are
related to this?
Anyone familiar with this Radiator Fan Time Delay???

Thanks in advance for any insight provided!!!!
Dave [Email: mastovsky.d@mellon.com]