There is a diagram on p. 80.16 of the Bentley manual, and that's probably
the only mention of it. There is no cable for the valve; You leave the valve
on in cooler months when you expect that you might want heat. The coolant
will be flowing through it, and you turn the blower unit inside on and off
as neseccary from the dashboard switch for that blower. There is an arrow on
the valve. One way is on, one way is off. But sometimes people have
by-passed the valve/heater entirely because either the valve or the heater
core was leaking.

Ed
> on my watercooled Caravelle (1989, 2.1) the additional heat exchanger
> doesn't work. I found a valve on it, in the water line, but there is
> no cable on it. It can be adjusted only by hand. Is this correct or is
> there anything that's missing in my car? I'm turning the valve in
> vain, the air that's coming from it is always cold. My Bentley doesn't
> say anything about the add. heat exchanger.
>