It was indeed low on R134a. I put 2LB in it.
It must have a leak in it. The coolant I used has stop leak in it - we'll see if it works....
The car is 13-14 years old and has never been charged. I'm not inclined to look for leaks just yet as whatever I find will be expensive to fix. I have my fingers crossed that I was just low and will be sealed by the new freon.