Thank you Steve for the reply. I just finished conducting the pressure test correctly at 2000 RPM's. Here's what I measured:
low side went to about -5psi
high side settled in at 200psi after about 10 mins of running
Center vent was blowing about 57 deg F; ambient outside here was 81F.
Interestingly, while attaching high side hose, I lost some precious elixir -- enough that the low aux fans would not kick in at all. I suppose this answers my question ... I need at least some freon added.
My earlier test had aux fans on continuously, with car in shade and about ambient temp of 95.
I'm gonna add some now ... should I be watching sight glass while charging or the high side pressure? I have 12oz cans (4 total). I would imagine it needs at least 1/2 lb, maybe a full lb.
'91 300E, 214K miles