DIY Guide: How to Diagnose and Replace a Bad Alternator with Ty the Car Guy

What’s going on guys? I’m Ty the car guy, and I’m gonna show you how to diagnose a bad alternator with the Enova 5310 and a pair of jumper cables. First thing we’re gonna do is plug in our scanner, the live data to check the battery voltage. And I know this battery voltage is gonna be a little bit higher. So I already diagnose this alternator. A good battery is gonna have around 12.4 to 12.6 volts at resting. Did charge it a little bit, but it’s sitting already a little bit low. 11,6,11,5. We’re gonna see what happens when we start it. Obviously no start. So go ahead and hook it up to our van right here. Red to red, black to black, positive first, negative last. Already you can see when hooked up to the jumper cables, the voltage went up to a healthy voltage of around 12.6 because it’s feeding off of the van. Go ahead and try to study. Just as I expected it went ahead and started. What we’re looking for now, a charging battery should be around 1413 volts. Keep in mind, this is reading ECU voltage. It’s not reading battery voltage. So it is reading 12,4,12,5, which is exactly what it should be seeing. We’re gonna go ahead and disconnect the negative battery terminal. And if this starts to drop, which it is, it means the battery is not being charged to supply the 12,12,6 current that it should be seeing, which as you can see it is dropping. Or another way to test this, hook this back up so the car doesn’t shut off, would be to go down here and do the alternator, battery alternator test. Connect this guy. And as you can see right here, it’s already reading below 12 volts. You should be seeing 14,13,5,14,3. And we know that this alternator is toast. The Auto Zone I worked at, what, 10 years ago, I started learning about cars. The first thing you want to do is disconnect the negative battery terminal when dealing with anything electrical.

And these ones are always fun. And the reason we’re using this bungee cord is that we don’t have to reposition the entire belt, saves us time, which saves us money.

Get all the wiring out of the way and now we can break loose the 14 millimeter fault holding me alternator in place. Once it’s broken loose, we’ll use our electric ratchet take over or watch so it doesn’t get scratched. So I don’t have the cover to be. And now we gotta get the bottom bolt which is the 12.

Alright, a little bit of pry bar action. Try that guy. Right? We’re going to make sure that our spacer is flush with the bracket. Oftentimes they don’t like to go in because this spacer is pushed inwards, but it looks flush today. So that’s great. Start with our background, feed it in by hand, catch a few threads. And the bottom one, you guys probably won’t be able to see. All right, started by hand and just before it finishes tightening, we’re gonna switch back to our 12.

I know what and go back to our 14.

And we’re gonna use that ratchet like this to snug things up. First time switch over 14. And that’s the. And since we bungie corded our belt, it’s as simple as getting back here with the belt tensioner, pushing down, keep popping our building. Had we taken the belt all the way off, we would have had to fully install the belt. And we’re just gonna pop it over the water pump a little bit more and just like that, alternator has been installed. Power cable. It is humid. Okay. She gets back on the mayor and just like that, we are done.

All right. And we are hooked up to the van, but the van is off. So the van’s battery is only gonna supply 12.6 volt as we’re given at gas, we’re seeing already 13.9 volts. And we could just do the test that it’s telling us to do, or we could just look at the voltage, but we’ll hold it over 2,000 for 15 seconds and it’s obviously gonna tell us that we have a good alternative. And as you can see, alternator is good.