Not sure about your SC, and perhaps this is the sensor you referred to, but
on an older Audi, the relay was switched by a sensor in the rad header tank
(i.e. NOT the engine temp sensor). Jumpering that switched everything on
immediately. I replaced that switch and made certain that coolant level was
correct and problem was resolved (I also installed an illuminated toggle
switch in parallel with the rad switch, which allowed me to both override
the temp switch if I felt I needed to, and see when the circuit was
energized - sort of the "belt and suspenders" approach)

Best of luck

"Ivan Cooper" > wrote in message
ps.com...
> >>Then I tried removing the fan relay and put a jumper wire in its place
> >>-- suddenly the fan started right up! I confirmed that the relay is
> >>just not being switched on (checked voltage on the relay connector at
> >>the fuse/relay box).
> >
> >If the relay is not relaying then it seems as though that would be the
> >problem. Sounds like you checked everything out very well.
>
> Well, actually the problem is, it's apparently not even *trying* to
> switch the relay on. I even put in a different relay and it still
> didn't come on (except that one time when it suddenly did but then
> wouldn't again). So it's not the relay, it's something further
> "upstream" like the fuse box wiring, computer (?) or something else.
>
> Unfortunately that's where I may need a little help or advice to
> troubleshoot properly! Thanks...
>
> -=Ivan
>