A charging system. What is it? What does it do? How can you tell if something is wrong?


A charging system contains 3 major components that all work together to keep the electrical system on your vehicle functioning. While all pretty simple, without all 3 working properly together your car will have a problem.

First, you’ve got your battery.

The battery, simply put, is what provides power to the entire vehicle. Your radio, interior lights, exterior lights, ignition system, the whole shootin’ match. Obviously charge in the battery needs to be maintained, and that’s where the next component comes into play:

The alternator.

This is the heart of your charging system. Much like a heart that pumps blood through arteries to the body, this little guy creates electricity and “pumps” it through cables to the battery. This part keeps the battery charged, and also keeps it from overcharging the battery through an internal voltage regulator/rectifier. A peek inside a modern alternator:

This will be the focus of the blog, but not before I get into the third major component of a charging system. The part that makes your engine turn over and start:

The starter.

This is what you’re hearing when you turn your key to “Start” before the engine fires. This little guy is responsible for taking a small about of power and making it a large burst of power to manually spin the engine via gears meshing together so that the internal combustion process can be begin, making the engine self-sufficient. The bendix kicks out and makes contact with the engine’s flywheel, turning the engine over. Here’s what a starter looks like inside:

When a starter fails, you may hear a single click when you turn the key, indicating a “hot spot” inside the starter where it gets stuck, or maybe a whirring sound, indicating the bendix spinning, but not kicking out making contact with the flywheel.

If you hear that single click, the common trick to get the starter to work is have someone hit the starter body with a large, solid object (like a hammer) while you turn the key. Sometimes this will knock the starter passed the hot spot and the car will start. This will only work a handful of times if at all, so if this happens, get it to a shop or replace your starter ASAP.

Now, how will you know you have a charging system problem? First, you may see this on your dash:

Maybe you don’t, but you still have other symptoms (like me). The subject in this case? A 1998 Pontiac Bonneville SE with 188k miles on it that I recently picked up.

If an alternator stops charging the battery, your vehicle will only run as long as the battery stays alive. When the battery starts dying, you’ll notice lights start dimming, the radio may cut out, turn signals get very slow/may not work at all.

This last point is what I noticed the other night when my wife came home with the car complaining that the turn signals weren’t working. It was night time, the headlights were on, the radio was on, and the A/C was on high. This means that the charging system had just about the most load on it that you could throw at it, minus the rear window defogger.

Now it’s worth pointing out that I’ve known that the alternator on this car was weak from the day I picked it up. With the doors open you could see the courtesy lights flickering, and when idling the volt gauge dips pretty low, like this:

At idle, each time the turn signal comes on, it stays on for far longer than it should:

If the engine is revved up slightly, the gauge comes back to about where it should be and the turn signals blink a bit faster. When driving, the gauge sits pretty close to where it should be, though I’d like it to be slightly higher:

Though I haven’t done the proper procedures for diagnosing a charging system failure (like testing alternator output), I’m pretty convinced I’ve got an alternator problem, so in true backyard mechanic fashion, I’m going to “throw parts” at it until it’s fixed.

The smart thing for me to do, would be to bring it to an auto mechanic I can trust *cough*Auto Works*cough* and have a charging system test performed on it.