Audi Repair: A4 Avant - Rear window wiper failure, wiper blade, ground signal

Question
I have a 1997 Audi 1.8T Sport Avant with a fault rear wiper. Before it totally failed it did judder. Having removed the wiper blade the motor doesnt seem to function.
I have a power feed going to one of the four wires, the Red and Black wire. I do not get any feed form the other wires.

I do not want to purchase another motor if it's not that. I am not sure if this has a relay or something else which may have failed.

I would realy appreciate some advice as to the sequence of events to try and track down the problems. Thanks.  

Answer
hi
the 4 wires usually mean: power , ground, signal and reference.
You have power and grond , there has to be signal from the switch (what's what I think). So I will check for signal from the switch. If there is no change when switch ON , you may have bad switch. I will check wire diag. on wed.
becouse I.m away for next 3 days.
good luck            pltech