So I've been having trouble starting my 2000 Alero (80K) lately and I've been looking at the battery or the alternator as the suspects. I hooked up a voltmeter across the battery and get a steady voltage above 14V (maybe 14.20) while the engine is running. Then I applied an additional load by turning on the fan and the heater and the volts steadily drop from 14.20 to maybe 14.10 in about 30 seconds. Suspecting a bad alternator I took it to a garage and showed the mechanic and it did exactly the same thing, dropping from about 14.20 to 14.10 when I applied a load, but the mechanic was unimpressed. He said it was not a problem, that all modern cars do that. Is he right?

 

That's normal. It sounds to me like the battery is the culprit.

 

Hmm, must be normal. There are how-to videos out there where they show the volts going down when a load is put on the alternator and that's supposed to show your alternator is shot, must be an old video. Now I hear it will go down to about 13.90 and stabilize. So I tried the test again and it seemed to go to a low of 13.82 and then climbed to about 13.87 where it stabilized. Might have the battery checked. Thanks!

 

Svnt442 is right, that is normal behavior. I would take a close look at the battery cables for corrosion, especially under the boots. Also look at the grounds.

 

It's a normal thing I guess. I heard about it too though I'm not exactly experienced it before. I think your mechanic is right.