I got a lot more help at Benz world than I di here. Seems to be mechancical minded group. Check this thread and it may help.
http://www.benzworld.org/forums/r170-slk-class/1323845-1998-slk-230-electrical-problems.html
My problem was the PSE box and I replaced it. I took it apart and cleaned it a couple times and it worked for a bit and crapped out again.

If after installing the new unit I had the problem of it not working after I turned the ignition off. I installed a battery cut off like this:


But even before that make sure you have a surge surpressor between your battery and the postive.

The problems I had after installing the PSE was...it was fine as long as I had the car running. As soon as I turned it off, I'd have to unhood the battery, wait a minute or so and reconnect it. Then it would work fine till I stopped again.

How did I fix this????
One night I came out to go to work and when I opened the door the courstey light was working....it's been fine ever since.

Don't expect a lot of help from these boards. Not that they don't want to help....but ....It's that if it isn't in any manual or book they don't know.

I've learned a lot about Mercedes Machanics in the last several months. They're about the same as the new breed of Harley mechanics.. Book smart.

If I can be of any other help please E-mail me.
Rev. Colin