vstech following the a/c thread in your signature led me to look at a temperature pressure chart.
From those charts and interpreting the readings chart it would seem like I have a blocked expansion valve. I have high pressure on the low side and low pressure on the high side.
Ill hook up the gauges this morn and update this post with the results.

Update. Engine off after overnight sitting 80f ambient
High 60psi
low 40psi

Running with a/c on
high 100psi
low 5 psi then 65psi then 5 again. I dont know what is going on there. I am starting to suspect that my high side gage valve is leaking.
Was able to get it to take a few more ounces of charge up to 45 or 50psi. Air from vents is still a couple degrees above ambient.


Another update: talked to my HVAC friend who said it is ok to let the low side gauge go up to 100+psi while you are charging it and this is natural. As long as your bottle off gauge reading of system pressure is in the regular range it is ok to have the needle up high while filling. This could change everything and would explain why I am not getting anywhere. When I try to charge I am turning it off before the low side gauge goes over 55psi or so.

Update once again: that seemed to do it. I have managed to get another half bottle in (around roughly 17oz total so far) and the high pressure side is coming up and approaching 250psi. Im now hearing the familiar squeak that the compressor has made for years and the aux. fan is kicking on.
The filling went real slow. So slow that I could not feel a temperature change at the bottle. I used the sight glass on the gauge set to show me if it was filling or not.
In the driveway I started seeing vent temps about 5-10f below ambient and on a highway test it got down to 65f out of the vents on a 90f day.

So this thing just might be licked. A couple more checks and modest fill additions to get the low side pressure to the target and I am thinking I will be back to regular performance.

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84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.