Hyundai Repair: Overcharged A/C??, proper air flow, internet explorer

Question
My wife's a/c started to blow not so cold.. it gets cold.. almost after a while but struggles to get there. A buddy at work suggested I recharge the refrigerant so I got one of the ones from the auto store and tried it. But when I hooked up the hose and took the pressure reading it showed that her sysem was OVERCHARGED.. how can that be? I've never put any in. Do all make cars use the same PSI levels for the a/c, or do some cars use different levels? She has a XG350, 2003.  

Answer
Whether the system is overcharged depends on what the gauge is trying to read.  It's possible the gauge is designed to read the system when it's running, in which case there are a large number of factors that affect the actual reading of the gauge.  One general indicator I use is that the pressure when the a/c is off should be about 90 to 100 PSI.  

You might wish to have the system professionally checked.  At the very least, don't add any refrigerant unless you know it needs it.  

One problem experienced by 2001-2003 Santa Fes, Sonatas, and XGs is freezing of the evaporator, preventing proper air flow and hence proper cooling.  Hyundai has redesigned the thermistor for the evaporator and published a technical service bulletin (TSB) describing this change and the proper installation of the new thermistor.  

You can view the TSB (#03-97-001) at www.hmaservice.com.  You'll need to register for a free account, and the site requires Internet Explorer.