Yup, its just a 3-way valve, one common port in the middle and two "selected" ports. When the knob is up, the common port is connected to one port, when the knob is down, the common port is connected to the other.

I actually bought one when I thought mine was bad, and mine turned out to be good, and the one I bought was the wrong one for my car anyway. I don't remember if its the black one or the white one (its probably the white one since that ones a good bit cheaper and I didnt know any better at the time), but if its the one you need, you can have it for the cost of shipping. I'll post an update when I find it.

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now