Ford Repair: mustang electrical problem, electrical question, meter test

Question
General electrical question - My daughter's friend has an 86 mustang and it has a problem with the electrical system. It seems to drain the battery overnight and we can't figure out why this is happening. It is so bad that it won't even accept a jump to start. The battery has to be charged for at least 15 mins. before it will start. We changed the alt. and the battery so far and it still does the same thing. Everything IS turned off that we can see. Do you have any suggestions on what to do next ? Thanks much !
Jerry Bozic

Answer
Hello and thanks for the question...I'll try to help.
 What you need to do is isolate the drain on the battery. To do this you will need an Amp/Volt meter to check for the draw. Disconnect the positive battery cable and place the meter test leads from the meter to the cable end. Have the AMP setting to about 10, and work back from there, until it is in range. Then start pulling fuses, one at a time, and look at the meter. The reading should be no more than 0.03amps........when you get it down to there, you have found what circuit the draw is on, and you can figure out what is on.
Hope this helps,
Erik