Jorn - sounds to me like you've done a pretty good job of working the problem.

I know nothing about Chinese potentiometers, but here's my take.

You've rounded 3rd base and are almost home. Buy one of those $15-$20 meters and see if it resolves the problem. I keep thinking about what Frank Reiner said in the 2015 post I pointed to in your companion thread. Lots of possibilities with an M103 CIS. I suspect SoCal is rich in automotive talent, but you could end up paying for things that don't solve the problem. That MAS unit ain't cheap.

If it were my car, I'd drop fifteen bucks and see what happens. If it works, you could then buy the $250+ unit from the Good-Better-Best seller in LA if you're looking for longevity.

Just my 2 cents.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"