[jessho]

The low side guage on a manifold has a pressure gauge and corrsponding markings below for the ambient temperature for that pressure for the different freons the guage is designed for. Otherwise, the correct pressure for the freon, when the system isn't running, should match the ambient temperature for that pressure, for that freon. If the temperature for that pressure doesn't match the ambient temperature, then the charge is wrong, which is most situations means there isn't enough freon. The lower pressure will indicate that the ambient temperature should be lower than it actually is. Low pressure will cause the evaporator to freeze intially. Eventually there will be no cooling at all, which usually is found when the low pressure switch on the dryer shuts the compressor down.

It the pressure is low, you have a leak, which will continue to leak until it's found and fixed. If not, and the evaporator coil in the dash is freezing, you're not getting enough air flow through the coils. I've seen this happen when critters get into the plenum and build nests, and I've seen it happen when the cabin filter gets really dirty, or the coil gets full of gunk from years of use.

I've never worked on a sunfire, but more than likely, it's not nearly as bad to get to the evaporator coil than most people think. If you're mechanically inclined, have a service book and a Saturday free, you can get to the coil and at least see if it's clogged, or there's a problem with a direction door. If there's a cabin filter, you should be able to get to it in a short period of time and change it without hardly any trouble.