Remove negative battery cable and hook a 12 volt test light between the cable and the negative battery post (it should not light up), if it lights up leve it hooked up and then remove and replace (one at a time ) the fuses from the fuse box and when the light goes out you have the culprit. Another way is to hook a amp meter set at 200ma the same way as the test light and look for voltage above the 200ma level, do the fuse trick, and when amperage goes to zero, you have the culprit