L7 questions

[Gloria and Mike McCollum <Stryder61@xxxxxxxxxxxxxxxx>]

I recently purchased an '87 L7 after having my e28 destroyed by a 40 mph
jeep, and I have several questions:
    1) What is that green warning light on the left side of the gauges?
It has 2 arrows facing outward and it         stays     lit until the
car is in motion...often following the battery light.
    2) This car has that late eighties 4spd ZF with that dial next to
the gear selecter...the owners manual does not explain exactly what the
1-2-3 setting is for. Is it some type of early semi-auto feature? It
seems like treating the transmission as if it was manual would be
harmful to its electronically controlled components.
    3) Under the hood there is a weird buzzing noise from this plastic
cylinder-thing directly behind the fuse-box.  It occurs while the engine
is running and when the ignition is at position 2 with out the engine
running.  It looks likes it's part of some type of a vacuum
system...there are a couple of small diameter hoses protruding from it.
I dont have a shop-book so i cannot seem to identifiy it or tell if it
is always supposed to make this irritating noise.
    Last but not least)  This car has a climate control system and the
A/c recently quit breathing cold air.  I know these cars are absurdly
high maintinance...so how cost are a/c repairs? i.e. compressors, etc.

thanx,

- -barT
    '87 L7 110k

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