atrain

So my car wouldn't start today as the battery was barely able to turn the engine. I go and pick up a new battery and then return to have them do a voltage check to see if the alternator is charging. I was just doing this as a precaution and assumed it was the battery but the tech told he was getting "zero voltage" from the alternator.

The car (2000) barely has 40k on it, and so it seems odd that the alternator could already go. I had noticed slower starts for the past few weeks though, but I assumed the battery was simply on the way out and so I wasn't surprised when it didn't start. Is there a way I can verify what the tech found other than driving and hoping I don't get stuck on the road somewhere? I couldn't even find another post from someone who had their alternator fail. Any help or advice is appreciated.

Slows2k

What kind of tester was used to check the alternator?

xviper

So what happened when you put the new battery in? Did start normally? Run normally? How did they "test" it so that they got ZERO voltage? If your car was running with battery installed, I can't see how they could get ZERO voltage. What kind of voltage did you get from the battery terminals when the engine was off? What kind of voltage did you get when the engine was just started? A good battery would give you around 12.5V to 13.5V. This would tell you that the battery is OK. If below 12V, not OK. With engine running, you would get 13.8V to 14.2V. This would tell you that the alternator is OK. If you get dropping voltage as the engine runs, then it's not OK. What did they do?

atrain

He had some kind of voltage meter that hooked up to the battery terminals. I'm not sure what all he did with that. It just sounded weird when he said zero voltage and made me question his results. I dont know exactly what he got with the voltage meter. I wouldn't really have known what to make of it at the time anyways.

And yes, with the new battery it started and ran fine. I'm worried that I could just be draining the battery if I kept driving it.

xviper

Unless he disconnected one of the terminals while the car was running and then checked the voltage, he did not get ZERO. And if the alternator was putting ZERO voltage when he disconnected, the engine would instantly die.
I think he was

If you get your own voltmeter, you can do the tests I posted previously and answer this for yourself.

atrain

Thanks, I think I will. Or at least go get a second opinion. Another thing I recall that was odd. When he was testing it he had me start the car. After I started it I started to get out and walk over to where he was by the battery and he told me to wait where I was. Immediately after, he declared his findings.

hmmm.

xviper

There's no way he could disconnect it that fast after you started it. And if he's using a voltmeter (which is likely), there is no way he could have got a reading of ZERO. He either has no clue what he's doing or he's about to try and sell you a new alternator.

ps. If you have the original battery in your '00 car, it's likely time that it needed replacement.