Testing alternator voltage

**UGotSmkd** · 01-13-2010, 11:37 AM

This is for a 2000 Silverado. I used a voltmeter and touched the red on positive and black on negative on my new battery. My reading with the engine at idle is ~14.5v with high beams, radio, etc. on. I did not apply any load. With the engine off, it was showing ~12.5v. Both of these readings were consistent each time I tried.

IDK, but I stilll have a feeling I am not getting a true reading by measuring the voltage through the battery terminals. I just wanted to know if there is another way to test it or is this method accurate enough?

**UGotSmkd** · 01-13-2010, 05:34 PM

Nobody has tested an alternator?

**G8GT721** · 01-13-2010, 05:40 PM

sounds right to me. autozone/advanced auto can usually test them if your trust them.

whats the problem your having, that you checking the altenator?

**GRRRR8** · 01-13-2010, 05:43 PM

Thats the correct way to do it. Your readings are good.

**UGotSmkd** · 01-13-2010, 05:51 PM

Originally Posted by G8GT721

sounds right to me. autozone/advanced auto can usually test them if your trust them.

whats the problem your having, that you checking the altenator?

Well, the battery I just replaced was bad and thought it may have affected the alternator. On top of that Charlie replaced the belt tensioners and idler pulley. It really quited down the noise in the engine compartment. The only thing unchanged has been the alternator, and it seems like I hear alternator whine, but maybe it's just the way these Chevy trucks are.

**UGotSmkd** · 01-13-2010, 05:53 PM

Originally Posted by GRRRR8

Thats the correct way to do it. Your readings are good.

Cool, BUT I didn't put any load on it, and from time to time the voltage needle will drop , but never below 14v.

**GRRRR8** · 01-13-2010, 05:54 PM

Originally Posted by UGotSmkd

Cool, BUT I didn't put any load on it, and from time to time the voltage needle will drop , but never below 14v.

If you had radio, hi-beams etc on, that is a load.

**UGotSmkd** · 01-13-2010, 06:01 PM

Originally Posted by GRRRR8

If you had radio, hi-beams etc on, that is a load.

Lol, true. What the hell was I thinking? I guess I meant to say I did not rev the engine while I was testing the voltage.

**Tjay74** · 01-13-2010, 06:29 PM

If you want load it down then turn everything on you can while taking readings.

Headlights, high beams, AC, seat heaters, wipers, stereo at moderate volume and hazards.

**todds87ss** · 01-17-2010, 01:45 PM

fan on high might be the greatest load, and a good test for the alternator.

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