When you have a fuse that keeps blowing and you cannot locate the intermittant short, you need to start adding fuses to the sub circuits. For example, if the cigarette light fuse keeps blowing and the same fuse feeds the dome light and the radio, add three fuses, one to the cigarette lighter, one to the dome light, and one to the radio. Make sure that the additional fuses are the same amprage or less. You will seldom have room to add the new fuses near the fuse panel. You will usually need to go somewhere closer to the load. You can find aftermarket inline fuse holders at almost any auto parts store. With the additional fuses, the next time it acts up, it will blow the fuse for the sub circuit and you will have narrowed down your search.