I'm not positive about the Jetta, but virtually all the cars with AC, kick it on anytime you use the defrosters. By using the AC to dry the air, the windshield will clear sooner, faster, at lower temperature and airflow.
While defrosters were designed originally to defrost(duh), they are used much more often to defog(dry) the inside of the glass. On tepid/warm rainy/humid days when the glass fogs in a NY minute, you can clear the glass without roasting and/or the fan on the drone setting.
You could live without it for the winter with a decline in some of the defroster/defogging performance,
BUT IF the loss of cooling is the result of a refrigerant leak, the system
may still operate. By that I mean the compressor may still kick on "thinking" it's still working fine. Some systems have a pressure switch that will keep the compressor off in the event of pressure loss.....some don't.
Easy enough to check, start the car, turn on the AC, observe the electric clutch on the compressor. The pully(sheave) on the compressor will turn with the belt continuously but when the clutch engages(with a loud click & visual clues) the compressor turns also.
Sometimes the loss of cooling is the result of a pressure drop in the system and not a complete loss of freon. If you have lost the freon charge, I'd yank the wire to the compressor as the circulating freon not only carries heat, it also carries the compressor lubricant.
There can be any number of reasons for loss of cooling and some them are easy and inexpensive to fix. That said the system will still probably have to be evacuated, leak checked(hold vacuum) and recharged. I assume it's too new to be an R-12(dichlorodifluoromethane) system and uses R-134a(1,1,1,2-tetrafluoroethane) which is much cheaper. That's good.
Sidenote- Leaking freon getting sucked into the engine comes out the tailpipe as phosgene gas. That's bad.
Don't worry about the international community getting on your case for a chemical weapon, as Bush will lie his butt off.
