2000 A4 A/C Issues...
 

Newb here, hope I posted in the correct area. Bet you pros can point me in the right direction.
Issue: A/C blows icy cold air sometimes (most of the time), but sometimes the compressor will not engage or will disengage. Sometimes I can begin my drive with the A/C working properly, then the compressor kicks off not to come back on. Other times, it will not engage from the start. Usually, if I turn the car off, then immediately right back on (no time for thawing...) it will work again. Both electric fans on the radiator are working properly. The car holds 1.1 lbs of r-134a, but I added some from one of the cheapie Autozone cans with the crummy gauge (do not have accurate pressures to report to you all, but low-side levels were in the green zone on the gauge. Have an appointment for diagnostics in a couple of days, thought maybe I could get a head start on it). It took about 1 lb of refrigerant. The issue does not seem to be related to ambient temperature.
Possible issues from my reading of forums on the topic:
1) Over or under charge of my system throwing hi/low sensors into whack mode and shutting it down (but why is it so intermittent?)
2) Hi/Low pressure (or trinary switch) switch bad - Also, it seems these would be connected to a schraeder valve and would not require evacuating the refrigerant... Is that correct?
3) Fan control module (but both electric fans work properly)
4) Cabin filter issue? (Doubt that given the correction during restarts)
5) Thermostat
6) Compressor/clutch (doubt that since it works so well most of the time, and again... the weird restart thing)
7) Moisture in my system (again, questioning the intermittent nature)
8) Part of the climate control electronics
I'm leaning toward a sensor/electronic issue. What do you think?