Air-cond compressor clutch question

[aka_juffa]

Ever since I have owned Snow White her air cond has never worked. With summer coming up I would like to fix this.

So far the following has been done.

System regassed. At the time the mechanic noted that the air-cond compressor clutch didn't have power. He wasn't sure if this was due to a faulty relay, gas pressure switch, or something else. I decided not to have any further work done at that time.

I have now checked both relays that sit behind the drivers headlight. They both appear to work OK.

Today I tested the air-cond clutch today as per instructions in my enthusiast's guide. While doing this I found a unconnected plug on a wire that runs to the air-cond compressor. I fixed this and can confirm that there is a magnetic field at the clutch.

I have two questions.
How can I tell if the gas is actually flowing through the system (air through vents is no cooler)?
Should the front cover/plate on the compressor clutch also rotate, or remain loose/still?

J