hello everyone> I've been having trouble with the charging system on this Impala after replacing the starter it started fine, then, the alt light came on. After driving a couple of miles the battery went down. I charge the battery then start the car and after a few minutes the alt light comes back on. At this point the batt. reads below 9V, and the cycle begins anew. I've checked the battery connections and replaced the alternator with the same results. I am hoping to obtain a code reader to read the codes while the batt. is charged this time. I'll post what I find. Any suggestions would be appreciated.

 

Code reader isn't going to do you any good, unless you have a check engine light, and that would be two different issues. If the wiring is hooked up as it should be, and tight (I've seen an electrical connector not plugged in on a new one with same results). Your best bet is to make sure you didn;t miss anything, and check output with a voltmeter at the alternator. My money is on (if the previous is ok with wiring ect), a bad alternator. Was the alternator you replaced with a new one?

 

I made an assumption that the belt isn't slipping on the alternator pulley, something else to make sure of.

 

alright I will check the hook-up at the alternator. I have notices there is no voltage between the alt + output and ground when the car is running and the battery charged. Also, the belt is ok.Thanks for the input!

 

Where did you get the alternator? Probably that's the culprit

 

You can also look at the field voltage at the alternator, I think the body control module regulates that. It's like the old voltage regulator.