How to Test a Car Battery Fuse
If your car's battery fuse has blown, you will need to replace it. However, this can be more complicated than it appears at first. Simply finding the fuse box can be a hassle for anyone who has not done so before. Additionally, identifying the blown fuse — or fuses, in some cases — can be difficult as well, as they can all look the same at a first glance. The following instructions can allow even a beginner to reliably identify a blown fuse in a car.
Step 1 - Find the Fuse Box
Use the owner's manual that came with your car to locate the fuse box. You should expect to find it either under the car's hood, or in some cases under the dash. If you do not have a manual for some reason, check both of these locations. At this point, you should attach your test light to the negative battery terminal, or another ground. If you are too far from your battery, a door hinge on your car will work just fine.
Step 2 - Identify Fuses
Once you have found the fuse box, open it up and take a look inside. Now that you have it open, you will need to identify the various things that you find inside of it. While there are many things in the box, your fuses are small, rectangular objects with one long dimension and one short one. Your fuses should be color coded by amperage, making them brightly colored and easy to pick out.
Step 3 - Set Up
Before you will be able to test your fuses, you will need to have current running through them. Insert your key into your car.
Step 4 - Test your Fuses
At this point, your fuses should be doing their jobs. Of course, if you are testing them, chances are that at least one of them is not. You can figure out which one this is with your test light tool. Touch the tip of it to one of the pieces of metal on the top of the fuse. There should be two such pieces of metal. When you do this, the fuse tester should light up. Next, repeat this step for the other piece of metal. The fuse tester should light up again.
If the fuse fails to light up the tester, it is damaged. Repeat this step for every fuse. Do not stop if you find one blown fuse, as it is possible for multiple fuses to blow at once.
Step 5 - Finish Up
Put everything away, and replace any damaged fuses. Be sure to use the same color.
This system will help you to identify blown fuses easily, but it is not always a workable system, especially if you are missing one or more of the required tools. While it is much harder, you can identify blown fuses with no equipment whatsoever in a pinch. Simply remove the fuses one at a time and inspect them for damage, which usually takes the form of blackening or a charred appearance.