Is there a way to test if my alternator is on its way out? Lately I've noticed my battery gauge dipping below 13v while sitting at a stop light and hovering around 13v while cruising. My battery was 4.5 yrs old so I bought a new one today, but the voltage is still dipping kinda low. My thoughts are the alternator is on its way out, but I can't be sure. What do you guys think?

 

Get a Voltmeter and check the V on the battery with the car running. You should have at least say 13V for it to be charging right. From what Ive seen at the garage, GM cars always charge stronger than other ones. Its not uncommon for GM cars to charge at 13.7-14.0V ... And its its not at at least 12.8-12.9, its not charging strong enough. Check to make sure you have clean connections on the alt. and battery terminals.

 

You can't go by the gage. If you notice what the gage reads when you have A/C and lights on, you would think the engine was off.

Incidentally, the reading across the battery should be 14V or over when the engine is running.

 

Thanks guys, I'll check it out today.

 

Most autoparts stores will test your battery and alternator while it's still
in your car for free. Some can even test additional items (staters, PCM codes, etc...)

 

Autozone will test it free.

 

I get the same thing when it is hot anbd I have a lot of accessories on. This has been going on for ywo years now (since I bought the car). As said above you can have your alternator tested and the battery tested but from the way you have described things, this is typical with the charging system for our cars.

 

I had my battery and alternator tested at Autozone, both checked out fine. I guess I just won't worry about it.

 

They can still check fine when tested, but if the voltage it less then 13 its not charging as much as it should be. Should be ok for a little while, but if it gets lower over time think about replacing it.

You can take apart the alt and check out the condition of the brushes and their contacts. if the contacts are a little uneven / not smooth or excessive wear of one of the two brushes then that means its soon time to rebuild the alt or replace it.

 

He said the voltage was 14v when he tested it, that's where it should be I believe.

 

I was having the same "issue" as you. Long story short, I replaced the alt and the voltage is identical to the way it was before. Basically a waste of $$ if your not having any problems.