A/C problems, Help!

[Scott McPherson <srmcpher@MailBox.Syr.Edu>]

Hi people,

I've been reading the archives and goofing around with the climate control
to educate myself as to how the thing works.  As of yet, I still appear to
be an A/C moron.  

When I start the car and turn on the A/C on LO, the compressor will kick in
and the air temperature exiting the vents will begin to drop.  This only
lasts a couple of minutes and then the compressor kicks out.  Then, no cold
air for anywhere from 10 to 20 minutes, followed by the compressor finally
kicking in.  The air gets cold (not real frosty - I suspect my charge is a
bit low) and the cabin will cool down nicely after another 10 minutes.
Sometimes the compressor doesn't kick in at first, but waits for  10 or 20
min, and sometimes when the compressor does finally kick in it stays on
(usually) while other times it is on and off intermittently.

Here is what I have done...

#1 - removed glovebox & inspected A/C programmer.  It appears to work fine,
moving the cable throughout the full range of motion.  Gave cable a good
shot of RemLube.

#2 - just for the heck of it, I removed the plastic cover above the firewall
in the engine compartment and found where this cable ends.  I removed the
remains of several seasons of leaves and gave the cable and linkages (for
the heater valve ?) a good dose of RemLube.

#3 - pulled relay from main panel under hood - checked it & also tried
playing musical relays with the other 40 ampers in there.  There is no sign
of any voltage going to the A/C relay.

#4 - unplugged wire leading to compressor - no voltage at all with A/C on or
off.

#5 - found the low pressure switch (under the plastic cover again) and
thinking that my slightly low charge may have something to do with this, I
jumpered the connectors to the switch .. still nothing

#6 - took wire leading to compressor & connected to 12V - well whoop de
freakin doo! the compressor kicked in!  Thus, it is not a problem with the
compressor itself.

#7 - had a beer, contemplated giving myself a good shot of RemLube.

Other various & sundry observations - please correct me if I'm wrong:

 - the gizmo behind the glovebox (the programmer, right?) only controls
water and/or air flowing    through the heater core and has nothing to do
with the compressor kicking in or out, right?

- there is another relay under the dash that can be heard clicking on when
the A/C is turned on (LO)
does this relay control the compressor, or is it the one under the hood?

- are there any electronic systems that disable the A/C if there is a
malfunction with the car? i.e. will the car disable the A/C if it thinks the
car is overheating?

- could the temp sensor inside the car be screwed up giving false readings
to the climate control?

- is my low charge causing this whole mess?

I guess it boils down to:  what is it that tells the FREAKING compressor to
engage?

Thanks....

Scott McPherson
srmcpher@syr.edu    5kcs      Frustrated, Warm, Clueless and Q-less in Syracuse.