This has happened very rarely, like maybe once in a 3 or 4 months: The coolant fan runs once the engine is shut off and will continue to run until the battery is drained far enough that the fan won't spin nor will the starter crank.

So I crack open my Bentley vol. 3 and scour the electrical diagrams for a possible answer. Now, I have a 1993 S4 Canadian which is actually a 1992 model.

Diagram X100 (92-93 S4) show that if I were to pull the relays sitting in positions 2 and 3, I should be able to open the circuit that powers the motor. While in a discharged state, I hook up the S4 to a jumpbox, lo and behold, the coolant fan spins up. I reach in the relay panel and yank out the two relays sitting in positions 2 and 3. The fan keeps running...grr.

(But wait, I notice there is a relay in position 1. Why is there a relay in position 1? According to diagram X31, the layout of the relay panel, "1" should be open for the 92-93 models...)

I pull out the mystery relay and the fan stops. YAY. I no longer have to jump start the S4 in the morning and afternoon anymore. But what did I disconnect?

Now, there is a relay in position 1 in the 1994 S4...well, there appears to be two groups of 1994 S4 diagrams.. i'm confused.

Anyone have any input? Are the diagrams for the 92-93 S4 incomplete?

In an earlier post I listed all of the breakers and relays that would cause this and had replaced them in addition to all of the thermostats. Trial and expensive error In the 95 S6 there is one relay in the box above the drivers feet. It controls the aux fan slow speed run on. If one removes that relay, the aux fan will run at high speed when the AC is on which it always did but will not run after the engine is turned off. Got tired of disconnecting the battary each time I went to the airport or parked the car. This problem had been going on for 6 months. I would not run the car for 3 weeks then all of sudden the fan would mysteriously start and stop. Hope this helps. I have determined that one of the leads to the relay is hot and when I get a chance will follow that back to determine what is causing it but as mentioned earlier have replaced everything that would make it hot except a possible short some where. In mine it is position 1 radiator fan delay time (kuhlerlufter Nachlauft) 214 part number 443951253K. It also looks like the diagram in the lid of the box show that this should be in position 1 which it is

Let me know if this works and if you find the real culprit.

Thanks Bob

I x-posted in the S-cars-list. Here is a response I got that shows how to fix the problem:

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We've been through this some times now, but I'll sum it up.
Yup, the relay 1 is the fan relay for 1st speed. (look it up at SJM's.)
But, better to fix it!
The fault is 99% in the after-run timer relay, a tall brown located
behind the passenger's kick panel. You 'll know it when you see it. The
relay is supposed to stop the fan after 8 minutes, if memory serves me
well. The fault triggers the output occationally. Mine started 'only
because it could' sometimes..
Try to yank this relay when the fan runs, and if it stops, that's it.
Replace or fix. (Often a small 2n2222-type transisitor alongside the
board, for those of you that own a soldering iron.)

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Here is a link to SJM's cooling site:

http://www.sjmautotechnik.com/cooling.html