Do SDLs have a monovalve?

Thats a similar problem I had with 2 of my cars. If it has one, try unplugging it/plug it in and see what happens.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!