I have a 95 blazer, and as soon as I turn the key to ON it blows the #4 fuse! Using a test light, I disconnect the negative cable from the battery, then I connect the test light clip to the negative battery cable, and then touch the test light lead to the negative side of battery! The test light lights up and then slowly goes out after a few seconds. If I remove the test light and wait 20 seconds, and then touch the negative side of the battery, it does the same thing over and over again! If it's a short, shouldn't the light stay on all the time? Why does it fade out??

Could a fusible link cause a fuse to blow, or would it just not complete the circute?