V8 radiator electric cooling fan operation

[Scott Mockry <scottmo@teleport.com>]

Ralph,

If you are referring to the electric radiator fan, and none of the fan
speeds are working, you may want to check the fusible link (70 or 80amp)
for the radiator fan. This fusible link is mounted in a small black box,
inside the engine compartment, on the drivers side fender near the front on
the V8. 

This fusible link is the same one as was used on  the 1990-91 Audi
100/200TQ. A picture of this fusible link black box from the 1991 200TQ
which mounts in a different location is shown at

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

There is a test in the V8 repair manual where you remove the connectors
from the radiator mounted fan temp sensor, and remove the connector from
the engine block radiator fan temp sensor, and insert a 400 ohm resistor
across the connector pins in both connectors, then start the engine and let
it idle. The cooling fan should NOT come on. Then remove the 400 ohm
resistors and insert a 100 ohm resistors across both connectors, NOW the
Instrument panel computer is supposed to step through  and turn on the 1st,
2nd, and then the 3rd speeds of the radiator fan.

(Yes, believe it or not, the instrument panel computer controls the
radiator fan)

I tried this procedure on another 1990 V8 and the radiator fan worked as
described above.

The radiator fan temp sensors in the block and lower end of the radiator,
should measure about 135 ohms with the coolant at about 100 C.

Relays #6 (medium speed) and Relay #12 (high speed) could also be causing a
problem.

Dyment Publications 1-800-544-8021 used to carry the V8 repair manual on
micro-fiche for about $30, the printed manual is no longer available,
although there are some copies floating around Audi cyberspace.

HTH
Scott Mockry

>My 90V8Q has a fan activation problem. The three stages of fan do not
>function and my technical goo-roos tell me that the problem is in a
>little processor module within the INSTRUMENT CLUSTER! If I want it
>right again I must shell out $1200.00 for a replacement instrument
>cluster...Ouch! Any listers been through this?
>
>Ralph Cook 
>90V8Q 194,000 mi, commuter wheels
>93V8Q  43,000 Mi, Sunday go ta meetin' car