my 92 grand prix battery discharge in just a day turned off, the battery and the alternator are new changed because of this problem, it doesnt discharge all days but in random days. if is a short, how can i check it?

I would start by checking the lights such as the trunk and glove box lights to make sure they go off when they are closed. If this is not the problem, get a 12 volt test light or volt meter and start pulling fuses. Apply the light across the terminals and if there is voltage while the accessory is off then that is probably where the short is. Remember that you can't do this with accessories like the dome light with the doors closed. If it is something that connects direct to the battery then you will need to check each circuit independently. Shorts are hard to find but they can be found if you work at it. As for it being on random days, I would check those circuits that involve areas where wiring can move or is subject to shock. That may narrow it down for you. Good Luck!

Also look to the charge post near the left front strut tower. they are known to corrode and cause all sorts of electrical gremlins. You can disconnect the negative cable on the battery and put your test light between the cable and the battery terminal. If the light comes on, there is a draw. Start by pulling fuses one at a time until the light goes out. Disconnect the ECM and radio fuses first as they draw low level current all the time for memory/clock etc... Once you find the fuse that makes the light go out, you have located the circuit drawing juice.

i found the "elec" or "elect" fuse (dont remember) was drawing .26 amps, i dont have the owner manual so i cant tell if its normal nor what is for