On the 1990 300 SEL:

I had the system converted to the new gas.
It has been blowing cool for the last 2 weeks and I don't notice any change so I think there is no leak. However, it is not COLD.

The shop was mad at me because I made them re-do some other work, so they were not interested in re-checking their work on the air conditioning.

I noticed in auto parts stores a rather inexpensive item: A small cylinder of the 134a, complete with a valve and a gauge on top, and hoses. A nice little all in one sort of product.

Since the system was just evacuated and refilled, should I be able to check the gas pressure and fill with a little more gas (if needed) myself?