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Eric
Eric, Automotive Repair Shop Manager
Category: Pontiac
Satisfied Customers: 30310
Experience:  20+ yrs. experience as repair shop manager and technician.
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Alternator won't charge the battery. Both are new 98 grand

Customer Question

Alternator won't charge the battery. Both are new 98 grand am
JA: How many miles are on the car? Will the battery hold a charge?
Customer: 200k yes battery is good
JA: Tell me a bit more about what's going on so he can help you best.
Customer: 3 months ago i replaced the alt. Battery died last week. Replaced that, it died within an hour. Just put another new alternator in charged the battery and it runs for awhile off the battery and dies
JA: Are you hoping to fix this yourself?
Customer: Yes
JA: Great! What have you tried so far?
Customer: Checked some fuses that's about it. Not sure what ones might have anything to do with it
JA: Is there anything else important you think the Pontiac Mechanic should know about your Pontiac?
Customer: No
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Pontiac Mechanic about your situation and then connect you two.
Submitted: 7 months ago.
Category: Pontiac
Expert:  Eric replied 7 months ago.

HI,

Ok, I need the vin number to pull the schematics for the charging system.

Also, do you have a voltmeter for testing?

Customer: replied 7 months ago.
A cheap one yes, but I'm not to sure on how to use it. 1G2NES52T8WM525219
Customer: replied 7 months ago.
It's T9 in the middle not 8
Expert:  Eric replied 7 months ago.

HI,

Ok, give me a few minutes to pull the schematics. In the meantime, I need you to check the voltage at the battery with engine idling and all accessories off(lights, ac, radio). To do this, set your voltmeter to 12v DC. place the red probe end on the positive terminal of the battery and the black probe end on the negative terminal of the battery. Then repeat with a couple of the accessories on. Let me know the voltage for both tests.

Customer: replied 7 months ago.
It doesn't have that there's a black v that has 2 20 200 600
Expert:  Eric replied 7 months ago.

HI,

Ok, if there is no DC setting then that voltmeter is only for AC, which is household current. If you can take a photo of the face of your voltmeter and use the paperclip icon on your reply box to upload to here and I can verify

Customer: replied 7 months ago.
Ok
Customer: replied 7 months ago.
Did you get it
Expert:  Eric replied 7 months ago.

HI,

hmmm, appears that it is only for AC voltage, ohms and amperage. We need one with a DC setting.

Ok, check and see if your blower for the ac/heater works on high. The high speed blower and alternator share the same fuse, so if the blower doesnt work on high speed it is a blown fuse, but if it does work, then that is not the issue

Customer: replied 7 months ago.
It does
Expert:  Eric replied 7 months ago.

HI,

Look at where the leads plug into your voltmeter. For the red(positive) are there more than one place to plug it in and if so, does one say DC.

Customer: replied 7 months ago.
Expert:  Eric replied 7 months ago.

HI,

Ok, put the black lead in the COMMON hole, and out the red lead in hole on the right when looking at it(see attached)

Put the setting on 2 on voltage and take your readings

Customer: replied 7 months ago.
It just said 1
Customer: replied 7 months ago.
If I put it on 20 it's just over 11 and dropping
Expert:  Eric replied 7 months ago.

Hi,

Ok, go to the 200 setting

Customer: replied 7 months ago.
11.8 with nothing 11.3 with everything
Expert:  Eric replied 7 months ago.

HI,

Ok, at the alternator, you should have a red wire, orange wire, grey wire and a brown wire. We need to test the voltage of each wire with engine idling and accessories off.

Test one at a time. You will place the black lead on a good ground(negative battery terminal works fine for this), and then you will need to stick the red wire in back of the connector at the alternator where each wire goes into in order to get a reading. I need the voltage for each wire

Customer: replied 7 months ago.
That's the only wires that go to it
Expert:  Eric replied 7 months ago.

HI,

So, just a grey and red wire?

How long have you had the car and how long has the charging problem been going on?

Customer: replied 7 months ago.
About a year. Change an alt 4 months ago. Battery light was always on but it just died this week
Customer: replied 7 months ago.
Just gray and red yes
Customer: replied 7 months ago.
Is it different for a v4?
Expert:  Eric replied 7 months ago.

HI,

Ok, the red wire goes between the alternator and starter. The grey wire sends a signal from the alternator to the engine control module(computer) that then goes to the battery light.

The 2 missing wires are critical. The orange wire goes from the fuse to the alternator to supply battery voltage and the brown wire goes from the engine control module to the alternator and is what sends the signal to the voltage regulator in the alternator to energize it so that it works. Without this, the alternator will not put out enough voltage.

At idle with accessories off, it should be registering 13.5 to 14.7v at the battery

Both the 4 and 6 cylinder engines have the same 4 wire setup at the alternator

Customer: replied 7 months ago.
How do I go about finding them
Expert:  Eric replied 7 months ago.

HI,

You will probably need to take the alternator off and look for hanging wires somewhere near it - one orange and one brown. If not anywhere near the alternator, then someone cut them really far back and from my end, it would be a guess on where they would have cut them.

Customer: replied 7 months ago.
Could I just run wires direct
Customer: replied 7 months ago.
I got the plug out and 2 are cut off right at it. I've followed the wires a long way and can't seem to find them
Expert:  Eric replied 7 months ago.

HI,

Yes.

The brown wire that goes to the ecm is actually a red wire at the ecm(they have a splice along the way and it changes color there). You will run from pin 74 on the BLUE connector at the ecm(see attached) to the L pin at the alternator connector(see attached wiring diagram).

The ecm is located behind and underneath the glove compartment(see attached)

The orange wire goes from the 30 amp fuse labeled HVAC BLOW MTR in the engine compartment fuse box(see attached) to F pin on the alternator

Expert:  Eric replied 7 months ago.

HI,

My suspicion is that once you run them, it still wont charge. I suspect that the internal circuit in the ECM that controls energizing the voltage regulator has failed and someone tried some type of workaround, of which there isnt one.

So just be prepared for the strong possibility of it still not charging after doing the wiring and having to get a new ECM.

Customer: replied 7 months ago.
Ok thank you I will try that tomorrow
Expert:  Eric replied 7 months ago.

HI,

You are welcome and have a great evening

Customer: replied 7 months ago.
If need be. Can I get an ecm from a junk yard and does it differ for engine size?
Expert:  Eric replied 7 months ago.

HI,

ECMs are specific for year, make, model, engine size and transmission. Also, it will need to be programmed with your vehicle's vin number and mileage, which requires a Tech2 GM scan tool to do so.

Expert:  Eric replied 7 months ago.

I noticed we have not yet resolved your concern you asked about. I would sure appreciate it if you would reply so I can offer my skills and knowledge and repair guide access to help as best I can.

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Expert:  Eric replied 7 months ago.

I noticed we have not yet resolved your concern you asked about. I would sure appreciate it if you would reply so I can offer my skills and knowledge and repair guide access to help as best I can.

~Do you still need more help?
~Confused by my info request or answer?
~Need more time?
~Confused on how the site works?
~Need more detail or a different explanation?

If the answer is YES to any of these just press reply and lets work on this concern some more.

If you have new questions now or in the future please do not hesitate to ask them. If you would like me to assist you. Just bookmark this page so you can access my profile easy and post a new question from the question box on my profile page.

Please remember to rate service using the rating page so that I may receive credit. Thanks

Please note that if you have a subscription service, you still are required to rate service, however you are not charged again. This is just so that your expert is credited for their time and services. Thank you.

Expert:  Eric replied 7 months ago.

I noticed we have not yet resolved your concern you asked about. I would sure appreciate it if you would reply so I can offer my skills and knowledge and repair guide access to help as best I can.

~Do you still need more help?
~Confused by my info request or answer?
~Need more time?
~Confused on how the site works?
~Need more detail or a different explanation?

If the answer is YES to any of these just press reply and lets work on this concern some more.

If you have new questions now or in the future please do not hesitate to ask them. If you would like me to assist you. Just bookmark this page so you can access my profile easy and post a new question from the question box on my profile page.

Please remember to rate service using the rating page so that I may receive credit. Thanks

Please note that if you have a subscription service, you still are required to rate service, however you are not charged again. This is just so that your expert is credited for their time and services. Thank you.