Over the last several years, the air conditioning on my E30 has gotten
>weaker and weaker. Now I can't tell if the air is any cooler at all with
>it on. Is this likely to need only a refrigerant recharge?
If you've run it down to THAT point, it probably needs at least a new receiver-drier because it has air in the system now. And almost certainly it has a slow leak somewhere which caused the problem in the first place.
--scott