Fresh air/Recirculated air

[MacGyver]

Hello,

I just bought a 1987 300E, my first Benz. There is a button on the dash which indicates recirculated air. When I push it, the light in the button lights up, but I can't seem to detect any other indication that it is opening or closing a valve. In my BMW 325 of the same year, you could hear an electric motor open a valve, very distinct. Does anyone know where this valve is in the Benz, and should I hear if it is opening or closing?

The A/C (134a) works GREAT...when I'm driving down the freeway, and it works ok at slower speeds, and almost ok at a stoplight. A friend suggested jumping the fan fuse (#7?) Has anyone else done this?