Dead Car Battery or Low Voltage Warnings Diagnose Battery and Alternator

Here we have a car with a low battery light on, and a bunch of low voltage fault codes. Let's get into it. Before we get into any of the codes, we want to make sure the battery or the charging system is working properly. If this is what's causing those codes, you're just going to be chasing your tail. Look at the battery. If the battery looks original, and the car is 10 years old, you probably need a battery, but take a look at it. Sometimes there's a date code. Batteries tend to only last five years and check the terminals. See if the terminals are loose or corroded.

These terminals seem tight. And then if you have a battery tester, test the battery. You can take a multimeter. Now, this isn't a great test for the battery. It just tests the surface charge basically. Put one terminal on the negative, and then one on the positive. And you want it to be about 12.6. Now, this battery needs to be charged up a little bit more. That's not a test. Like I said, you need a battery tester to test the battery to see whether it's a good battery or not. At this time, we're just gonna charge it up, get it closer to 12.6.

As long as it's above 12.3, you're probably okay but, just in case, we'll charge it up. Before we start the vehicle, you want to just take a look at the alternator. Make sure it's still there. Make sure no one stole it. Make sure the belt is on. If the belt is popped off, it's not gonna do its job. Take a look at the wires and the connections. Make sure it's not loose or anything. Okay, with the battery charged up above 12.6. Now, we're gonna hook up the bolt meter, and I'm gonna start the vehicle, and we'll see what we're at.

When we start the car the voltage is gonna drop temporarily. You want it to stay above 9.5. With the car running, you want to make sure the voltage is above 13.5, and in our case, it's below 12 volts. Normally, these symptoms point to the alternator. There could be other problems with the vehicle. There could be a problem with the wire that goes from the alternator to the battery, and also, the signal that turns the alternator on.

The alternator is a common problem on this particular vehicle. So, we're gonna go ahead and change it, and check the results afterwards. We've got our new alternator in. Now, we're going to check it out. Make sure it works. So the voltage was way over 13 volts while it was running, which is exactly what we wanted. So this car is all set. If you enjoyed this video or it helped you out, make sure you subscribe to our channel. Ring that bell. Turn on all notifications so you don't miss any of our videos.