Ok.... feel free to yell at me for not doing full search of the 72 pages of this post

(with thanks to the original author of the thread!)....
Want to start by saying a couple years back, noted my temp gauge was wandering away from my very German rock solid straight up and down (90C I think?) so I did the test, Sure enough, one fan was not working and because of the age of the car I just tossed in two new fans. I don't recall how much testing I did after that and because we have only a few limited hits of 40c or 100F plus encounters I had not noted any issue (and yes the AC works)
Recently in Washington State we had some extended trips in 105f + and noted the gauge was again doing a bit of a climb and for the first time noted the AC cut out (momentarily), as the temp dropped back to normal AC, again was running fine.
Now, AC is a bit of a mystical marvel to me but as I (think) I understand it, low refrigerant, under extreme temps will go "high pressure" and my AC will cut out (safety)? Or am I looking at this the wrong way, is it possible the AC is cutting off because I'm having a problem with the high speed portion of my fan setup (as it seems to have taken place exactly at the point the high speed should have turned on based on the specs of the thermal switch). I do recall testing my original switch and for one reason or another have a brand new one sitting in my spares (I get the feeling I was suspicious about the thermal switch test). For that matter, it may also be a fan control relay?
As my TDI is a 2005 and I know the AC has never been serviced its likely refrigerant is low, but the AC is working. Like many others I love to get it pulled and refreshed but lately shops are so backed up and hack about not wanting to touch anything "that old" I have not located anybody I can trust. I would do it myself, have the gauges/pump and stuff (an of course willing to have the old refrigerant recovered) but being in Canada, all the consumer can get their hands on is 12a (too funny when I mentioned this to a mechanic in the local hick repair shop in central WA.... he had never heard of the stuff... nice enough guy, handled my Suzuki no problem but was not sure about the Jetta).
I did dig around my notes, normally I download and keep some of the precious information available on this forum as I was sure I had a relay diagnostics someplace... if anyone has a link that would be great!
In the meantime, could someone confirm I'm on the right track with either "no high speed fan" and or "low refrigerant" causing the minor heat engine temp rise in extreme heat?
Thanks
Martin