Every automotive has an electrical system that consists of three very important components: the battery, the starter, and the alternator. All these systems work together in a cyclical way, so an electrical problem that starts in any one of these components will affect the other parts of the system. It is important to check it on a weekly or even daily basis to make sure that future problems will be prevented.
How will you check it? So basically just hook it up. And make sure you get a good bite like rock it around so it goes through the corrosion. And I mean it tells you right now the battery voltage.
When to check it ? You must have your vehicle's electrical system checked immediately if: it won't start – you turn your key and hear clicking, grinding, or no sound at all. Interior or dashboard lights do not illuminate properly. Your vehicle runs well, but the headlights dim while you're traveling at low speeds, or idling at a stop.
If you notice a voltage drop across the fuse then that is the circuit with the chart. And this way you can find any short in any modern car without even having to disconnect the battery. Your vehicle might have a loose electrical connection. A blown fuse will cause problems. Sometimes, it's that one part of the system is constantly drawing power, even when the engine is shut off, and it slowly drains the battery. Perhaps the most common cause of car electrical problems is that the battery is failing. Better check your car electricals as soon as you Notice these problems.