1991 Audi 100 with high idle

["Norman, Victor J" <VNorman@SIKORSKY.COM>]

Can any of you technical wizards help me with the following problem?
I have a 1991 Audi 100 that runs fine except...it insists on idling at 1400
rpm. 
Turning the climate control on or off doesn't affect it, so that isn't the
cause.
Unplugging the electrical connection to the ISV brings the idle down to
800rpm
so I'm assuming that I either have a bad ISV or (more likely) the signal
into the	
ISV is high. Is it possible to measure this input voltage with a DC tester
or does
it require an oscilloscope? What input level should I expect to see. If it's
high,
any guesses on why?  If the problem is the ISV itself, is it repairable?