Just got new code on 93 Transport 3.8 injected engine.
book days overvoltage. is this a problem with the alt. or elsewhere.
check engine light will go on and off. Need to know what I'm looking at as in repair for this.

DTC53 is EGR problem - nothing related to overvoltage - I have the same for a long time. EGR valve has 3 electrically operated valves. Depending on load/speed/temperature condition, various combinaison of the valves are required. One of yours is faulty: when the faulty one is not required, your check engine ligh turns OFF. Any combinaison that requires THAT valve - and it does not operate - then you have the little light ON.
If you have no driving problem, then it means it stays closed - otherwise you would have idle problems. SO you can live with it as long as you want...except in certain load conditions, you might not match EPA requirements.....Correction requires that the EGR valve assembly be replaced- front of engine, driver side - Cost about $150 US$ + labour

sounds like your voltage regulator is stuck. Since it's part of the alternator, it's time to replace it.

CHeck these:
www.avigex.ca/egr1.jpg
www.avigex.ca/egr2.jpg