Trans control V*

[Ralph Cook <bluesgtar@redrose.net>]

This is my first posting so bear with me.
I own a 1990 V-8 Quattro and in the past six months have experienced the
failure of the transmission control box. The car shifts int "limp home"
mode which is 3rd gear only and the selector lights up all positions.
Huber's Auto service New Holland PA has; 
1. Pulled the box, cleaned the contacts and solved it the first time.
2. replaced with a used control and solved it the second time.
3. Have it today saying they don't know what is causing it. Could be
anything from frayed wires to just bad luck.

Is there any similar experience out there? 
Is there a test of the box itself?

Ralph Cook
Denver, PA
bluesgtar@redrose.net