Lee,
I will suggest to check for power at the vacuum pump (under the rear seat, passenger side).
Chances are the problem is that infamous + connection under the front passenger seat. It is well documented.
A search for posts will lead the way (If I remember correctly I posted about this a while ago, with pictures). Do a search for posts by me, you will find it.

Edit: Added title of post.

"Help me find this positive voltage distribution point"

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
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