You need to send this question via email to a gentleman in Morro Bay California. His name is Peter Staford, he's an electronics engineer that remanufactures and reengineers a variety of electronic components for european cars, specifically mercedes first and others second, only because the others use the same VDO components or what ever brand mercedes uses and the net covers them all.
His company is called:
GENERAL DEVELOPMENT LABORATORIES
DEDICATED TO INNOVATIVE METHODS AND SOLUTIONS
Since 1981
http://www.gdl-online.com/begin.html
[email protected]
Keep it short and to the point, he works in a very small shop and is very busy.
Peter has done 2 amps for me that have worked flawlessly for years. If you send him the amp and the actuator, he will guarantee them for life. He knows more about how these thing work than mercedes does, and he's made them better because the original units suffer from several design flaws that he has meticulously corrected through failure analysis and assessment, reverse engineering and extensive testing. If you have any understanding of electronics, after a short discussion with Peter, you will instantly realize this guy is the best. He has a perfection problem in that his work that he returns to you has to be just that, perfect. His prices are way reasonable and the end result is way better than new.
good luck.