A/C HIGH bouncing - Blockage?

[mikes603]

https://www.youtube.com/watch?v=yJJqNlftFlg

Here's a video of my R53 (new owner) running with an AC manifold attached. Notice the High side bounces from 150 to 250psi in a cycle with the fan kicking on. Low side wanders around 30psi. Shop was at 60degF

AC blows cold but not freezing cold. Maybe 50degF (I need to put a probe in a vent still).

Does this indicate a blockage at the expansion valve? Or is there a sensor that runs the expansion valve that could be faulty? Or do I have a non-condensable in the system?