Charging System Failure after replacing alternator

Recently had an issue with my Alternator where it had a chunk of metal lose inside so I ended up replacing it with a brand new one from AutoZone. Recently, after only a month, I am running into issues with my car having a “Charging System Failure” I took it to AutoZone to test the battery and alternator and they said my battery was bad. One battery replacement later, that didn’t work. I ended up replacing the the terminal connector to the positive post, still didn’t work. Any suggestions?

A few things to note is my car can make it a long distance but it runs on the highway between 11.48-12.09v it will have an occasional spike and hold at 14.2v after a good 20 miles. Then I stop the car go and fuel up and start it back up at it’s back to 12.09. Everything is new with the Charging system: Alternator, Battery, Positive Terminal connector, and Serpentine belt. I’m not really sure what else to do in order to fix it. I am going to take it back to AutoZone and see if they still say it’s the battery of course but prefer an opinion on the topic here.

AutoZone is in the business of selling parts they are not mechanics you need to have an independent shop look at it.

You don’t say what year your Pontiac is, but some GM vehicles have a battery current sensor on the negative battery cable.

2008 Grand Prix intermittent "charging system failure" and "battery saver mode" on DIC. The dealer I bought the car from

When these fail, the charging system can act erratically.



It’s a 2007 Pontiac Grand Prix GT. I did see this on the negative cable. Is there any way to test this sensor? Or do you kind of just replace and hope for the best?

You replaced everything else.

Why stop now?

Replace it.


I’ll give this a try and reach back out with results.

On a side note, I have had a new alternator fail from autozone a month after I bought it. voltage was all over the places. low to overcharging.

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There could be a problem with the current sensor possibly. I don’t know how the charging circuit is using that sensor in the charging circuit so I can’t help you much with that. You should be able to check the resistance of the sensor and get some sort of reading, but I don’t know what a normal reading should be. As a guess I would suspect a fairly low resistance would be normal.

I suspect the problem is within the replacement alternator, since that was changed out and worked for a while at least.

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You might check the junction terminal connection. GM vehicles generally have a main fuse or junction terminal connection and all electrical power except the starter motor windings go through that junction.
With age and being located near, or under, the battery the connections get corroded and can cause things to become erratic or flat quit. There should be a lead from the alternator to that connection.

SAAB (part of GM) also had this issue. While in CO in a SAAB I used to own I checked into a hotel. Came out and nothing. Everything dead but I kind of had an idea. Cleaned the junction terminal and all was well. Note to self. Check that before leaving the house…

My son also had this issue once on his 1996 Camaro but like the SAAB it’s easily diagnosed and fixed.

You removed alternator. So you flexed all wires. The charging cable and the sense wire cable that controls alternator. They were untouched before you changed alternator. Could be as simple as broken wire inside connector. Happened to me. Had to replace plug.

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The charge voltage when driving is too low. Either something in circuit is loading the alternator, or alternator or its charging circuity is faulty. Suggest to start with this diy’er charging/battery test: before first start of the day battery should measure about 12.6 volts; then immediately after starting engine, 13.5 - 15.5 volts. Post what you measure here, you’ll likely get more ideas.

Do you have any high electrical power aftermarket equipment installed on your car? Stereo amplifiers etc?

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I went ahead and replaced not only the Battery Current Sensor, I also ended up replacing the negative battery cable.This didn’t positively or negatively impact the current issue.

I will give this another try. I have no aftermarket equipment installed so thankfully can rule all of that out. Originally it was starting at 11.9 and kept a charge as long as I didn’t use say the AC or the RADIO or the power windows. Now it’s down to 11.1 and is decreasing more and more every time I start it.

Have you checked for continuity between the alternator and battery? Just wondering if the fusible link has popped.

Measuring voltage at the battery + terminal? Measure it at the heavy red lead on the back of the alternator also. If you have 11ish at the battery and 14ish at the back of the alternator then check the fusible link.

You say new alternator but does that actually mean new or is it remanufactured?
With key on and engine not running check for voltage at the small red wire lead on the back of the alternator. No power there means the alternator will not charge.

You won’t be able to even crank the engine soon w/this trend. Suggest immediate att’n required.

Ask the folks where you purchased the “new” alternator if they have an alternator test fixture. If so, that’s the next step. My guess, faulty replacement alternator. Faulty electrical parts right out of the box pretty common by reports here. I’ve been given 2 faulty Corolla starter motors, failed right out of the box. Auto parts store units. If testing shows your alternator is the problem, suggest to buy another either from a GM dealership, or if from auto parts store, an AC/DELCO rebuilt unit.

This is something I have not done, I thought they would do that at Autozone but it seems they only tested the battery current, I will go buy a multimeter and check it. The alternator was remanufactured, did not know this until checking the listing.

Yeah, it doesn’t even crank anymore sadly. Sorry by new I meant remanufactured, and they said they can only test it on the car but I can’t even get the car to get there without a tow. I will call other local car part stores and see if they have this fixture you are speaking of.

Since you are buyng a multimeter anyway,

Since you are purchasing a DVM (multimeter) anyway, one option is to remove the battery and charge it with a battery charger overnight, then re-install battery & use the DVM to do this test: Before the first start of the day, battery should measure about 12.6 volts; then immediately after starting engine, 13.5-15.5 volts. The second measurement tests the basic alternator function with engine idling. If you report your measurements here, you’ll likely get some more ideas.