Auto Air Conditioning & Heater Repair: 99Escort hot air from AC, electronic leak detector, pressure gage

Question
I own a 1999 Ford Escort 4 Door.  I was in a parking lot waiting for my husband with the car and AC running.  We were cool and comfortable, after about 10 min the AC started to blow hot air.  My husband got a Freon kit and checked the pressure and it was showing to much pressure.  When I turn on the AC now it will blow out cool air for about 30 secs and then hot air.  What should we be looking at to fix this?  

Answer
The pressure can ONLY be checked via this method with this LOW SIDE pressure gage on the LOW SIDE pressure port while the compressor is RUNNING.

Without more info, It appears as though you have a leak in the system that will need to be located using an electronic leak detector.