Audi 200 multifunction woes

[mike posner]

I'm in the process of replacing my multi -malfunctioning
switch for the for the fourth time in 6 years as  my h2o guage
has gone south again.  I am also unable to get current to
my ac clutch which has been recently replaced. I have been
studiously reading the large amount of material on diagnosing  the a/c system and Im, getting lit up on 3, 5 and 7 on channel 7, and channel 3 only on channel 17, but this somtimes has read 3, 5, and 7 as well.. I plan to replace
 the  mfts, but have some concern in that I'm getting 
3.4 volts off the temp wire (T) as well as 12 volts off the (+) wire which is ok.   Should the T wire (y/brn)  show voltage
or does this suggest a short from the ac control panel?

I'm concerned about blowing out a new sensor  by exposing the temp wire to voltage that shouldn't be there. I also rewired the 4 wire plug making sure the right wires were
going to the right functions, noting that the sensor has
almost invisably marked T,R,C and + over their respective terminals. 

TIA  Mike