Bad Alternator vs Bad Battery
We have all been in situations with our cars when we try to start up the engine, but the car won’t start. It’s easy to misdiagnose a power problem by thinking we have a bad battery when we really have a faulty alternator, or vice versa.
So, how can you tell if it’s a bad alternator or bad battery and how do you not make the mistake of replacing the wrong part? Let’s look at a few ways that you can tell which components is giving you this problem.
Signs of a Dead Battery
When you notice that you’re having power problems, the battery is the first thing you should check. Fortunately, almost all newer cars and trucks have computer diagnostic systems built into them which will let you know if you have low battery power.
But you shouldn’t always rely on them because they don’t always give you the right information. For starters, have someone give you a jump-start to see if it gets your car running. If it does, this means you have a bad or drained battery.
Depending on the battery’s age, it may simply need to be recharged (for instance if you accidentally left the headlights on) or you may need to purchase a new car battery (if the current battery is a few years old).
Other things that my indicate a dead car battery include: an engine that is slow to crank but eventually starts, electrical systems such as headlights, power windows, and windshield wipers don’t work as well as they should, and the car battery warning light illuminates in your dashboard.
You should also make sure there is no corrosion where the battery cables connect to the battery and that everything is tight. Either one of these would indicated a bad battery even though it’s simply a connection issue.
Signs of a Bad Alternator
If you have a failing alternator, your car will show symptoms like dimming lights, strange sounds, and even strange smells while you are driving. When you jump-start the vehicle, it typically won’t start up in this circumstance.
So, when a battery is forced to do that, it will wear out quickly and you’ll literally have minutes before the battery is fully drained and needs recharging. But in some cases, the opposite happens when the alternator begins overcharging and electrical components may start to fail. Before troubleshooting the alternator itself, make sure it’s not simply a blown fuse.
Recap
A lot of people find out the hard way that even though they purchased a new battery, they actually have a bad alternator. They’ll put the new battery in and the car will start up just fine. But then when they pull out of their driveway, the car will conk out by the time they make it around the block.
Similarly, the vehicle owner may assume it’s a bad alternator since their battery isn’t too old and then spend a lot of money replacing or repairing the alternator which didn’t need fixing in the first place. Even though car batteries come with warranties (ie: 48 months, 60 months, etc.), it doesn’t mean they will actually last that long.