This is a common problem on 210 air conditioners. It is caused by insufficient refrigerant flow in the evaporator.

If the compressor were malfunctioning, I would expect to see a higher reading on the low-side. That seems like a very expensive "first step" to take.

I've seen one example on this forum of a plugged receiver causing this problem, but that was on a '96. I think I also have a plugged receiver in my '96, but I haven't evacuated the system yet.