Car Shuts Off – Is it the Battery, Alternator, Something Else ?

Car Shuts Off – Is it the Battery, Alternator, Something Else ?

Hi. I’m Steve and I’m not a professional mechanic and this is not intended to be a how to video. It’s just my personal journey going from a completely stocked 2002 Tahoe to a heavily modified 2002 Tahoe and all the little fixes that I needed to make along the way. I like to make these little videos because when I take stuff apart they help me to remember how to put stuff back together again. So, if somebody’s watching this can learn from my mistakes not make the same mistakes themselves, I feel like it’s worthwhile. So, here we go.

All right. So, we’re happily driving along in our car and we notice that the battery light comes on. There it is right there. And also notice it is below 14. So, while running that’s not necessarily a good thing. So, a couple issues here. So, the question is is it the battery? Is it the alternator? What to do?

Typically, with the engine running the alternator charges the battery so that that would be above the 14 Mark. And as you can tell we got squat and we got that light right there coming on and off and on and off. So, we turned her off. She starts up fine which leads us to believe that our battery is okay but we’ll do some further testing but I’m going to go ahead and kill this thing right now. So, the first thing I want to do is check the voltage; set volt meter, put it on DC 20 and red to red and black to black and we do seem to have a charge to our battery, so our batteries got juice.

All right. So, a couple of things that we know so far is it starts up fine which eliminates any potential problems with the starter and I’m not so much thinking the battery anymore. So, my attention shifts over to the alternator. Now people will tell you in order to diagnose an alternator issue all you need to do is fire up the car let it run and then pull the negative cable on the battery and if it dies then it’s definitely the alternator. The problem is that in newer cars with all the computer controls and everything like that you could potentially cause more harm than good. So, although that will work especially in older cars, non-ECM cars from everything I’ve read it’s ill advised. So, what I want to do is I’m gonna check a few things on the alternator and notice this alternator is brand new so why in the world is it giving me issues? So, I want to check the connections. That connection is good. I’m gonna make sure that the connections are nice and clean. That’s pretty solid right there. Follow that wire to this little box right here and that connection is good and solid and clean. We’re going to continue to follow this connection all the way to the battery and all of our connections are good, they’re solid, they’re clean. So, the next thing I want to do is I’m going to fire it back up and make sure that the belt’s not slipping here and that it’s actually turning this. So, we’ll go ahead do that next.

With it running that ultimately should be charging our battery but it’s not. So, eventually this battery is going to die. So, I’m going to go ahead and kill it. Okay. So, luckily for me I was able to find a receipt and this puppy is going back it’s only six months old. Always undo the negative battery cable when working on your car stuff.

Okay. So, Napa hooked me up with a brand new one and I’m going to go ahead and throw it in and see what’s up.
All right. So, I got the new alternator in place and I got my belts back on. Don’t forget to plug the electricals back in and obviously there’s a connection back here and batteries back and connected and when we fire it up you can see we’ve got past 14, so that’s charging. So, we’re good.