A/C, Radio, Arrrrrg!

[Elliott Potter <epotter@abraxis.com>]

OK, I think this is my last attempt to be civil while working with these
problems.
The car: 1993 90CS (USA)
The problem:
   a) There's a puff of static from the right rear speaker (woofer)
every time you turn the radio on or off.
   b) The A/C works intermittently.

Both of these problems have existed since we bought the car, brand new,
almost 4 years ago.
The radio head unit has been replaced 3 times, and each rear speaker has
been replaced 3 times.  Still happens.  A while back I experimented with
some cardboard, and voila!  The sound dissapears--it seemed that the
cardboard insulated the amplifier board from its metal case.  Or so I
thought--more on that later.
The A/C works perfectly in temperatures up to about 75-80 degrees F.  If
the interior of the car gets hot, though, the compressor won't turn on. 
The little "snowflake" won't turn on, and you can hit the A/C button
until your finger falls off but it won't do any good.  This has the
dealer totally stumped, they've replaced about half of the system to no
avail.  I'm now on a first-name basis with most of the people in the
shop.  Last time I took it in for it's routine service (hey, there's
something wrong with the A/C!) the service manager himself did the
service; they did some rewiring in the climate control head that is
evidently something they do on the 96 A4's.  Does anyone know what this
is?  It didn't work, and now the climate control defaults to 71 degrees
F with the A/C on (if it's working today) every time you turn the car
on.

Another problem with this new setup is now, *every time* I turn the
radio on or off, the static noise from the rear right speaker happens. 
This hadn't happened for almost a year, and as I was driving out of the
parking lot after the dealer fiddled with the wires, it happened.  It
has happened every time since.

Any thoughts?

Sorry for the long rant

Elliott