1997 A4 Reay Washwipe

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 power 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. What's the best way to test the motor, use a temporary feed to one of the cables?
I would realy appreciate some advice as to the sequence of events to try and track down the problems. Thanks.
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