check engine light

Just purchased a 94 Intrepid, she has been running just wonderfully with the exception of the check engine light and the A/C fan switch. The light comes on after about 15 minutes of normal driving, the temp indicater reads cool, have no clue what is going on.
The a/c fan runs only on high setting. I am assuming this is simply a bad switch that needs to be replaced. Anyone else have the problem with the check engine light?

if you want to find out what the code is, turn your key on/off 3xs ending in the on position, watch the check engine light flash, if it flashes twice then pauses and then flashes another four times, that's a code 24. Visit this site for a definition of the code. (http://www.automotiveforums.com/vbulletin/showthread.php?t=355082)

found 3 codes, 12, 21, and 32. Standby memory circut, o2 sensor, and open or shorted EGR tranducer. Any of these problems "fatal" or can they wait to be fixed? Thanks for the info, much appreciated.

12 is a normal occurance if the battery was disconnected, that will go away after a while. 21 means that you have a problem with the O2 sensor circuit or the sensor itself, if you have more than one sensor you have to figure out which one has the problem, I wouldn't let it run that way too long, if it is running rich you could heat up the converter and give yourself even more problems as well as your fuel economy will suffer. 32 means the EGR transducer/solenoid went bad and needs replaced, not a cheap part because the EGR Valve also comes with it, since it's also an emissions part I would also not run it too long before changing it.