Alternator not changing?

Tiny
BRODYWINTERS1005
  • MEMBER
  • 2003 CHEVROLET MALIBU
  • 3.1L
  • V6
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
Alternator not changing battery has 2 pin connector and alternator is 4 pin.
Sunday, June 22nd, 2025 AT 6:13 PM

20 Replies

Tiny
STEVE W.
  • MECHANIC
  • 14,726 POSTS
There should be a large red cable that connects to the battery stud. Then orange, gray and red wires that go into the connector for the alternator. The D wire is a feed to the alternator that tells it the system voltage at the fuse box. The gray wire is the Field control wire, it tells the alternator when to charge. The L wire is the circuit that tells the PCM if the alternator is charging and turns on the light in the dash if it isn't. There are 4 pins in the alternator but only 3 are used. The first thing would be to have the alternator tested. Then if it is the issue, replace it.
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Sunday, June 22nd, 2025 AT 8:27 PM
Tiny
BRODYWINTERS1005
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Okay, I have an org and red wire but no gray. Where would I locate the gray wire to find it?
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Monday, June 23rd, 2025 AT 9:59 AM
Tiny
STEVE W.
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It should be in the same harness as the red and orange if they are bundled.
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Monday, June 23rd, 2025 AT 12:52 PM
Tiny
BRODYWINTERS1005
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So, I should be able to follow the org and red wire and find the gray, correct?
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Monday, June 23rd, 2025 AT 12:59 PM
Tiny
STEVE W.
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It should be taped in with them if it broke off or was a rodent snack. Or if you want to find it faster just go to the PCM under the dash and look at pin 29 on connector 1.
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Monday, June 23rd, 2025 AT 6:27 PM
Tiny
BRODYWINTERS1005
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Okay thanks, I will try in the morning.
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Monday, June 23rd, 2025 AT 6:33 PM
Tiny
STEVE W.
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Let us know what you find and we can go from there.
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Wednesday, June 25th, 2025 AT 4:57 PM
Tiny
BRODYWINTERS1005
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I looked under the dash and found a grayish black wire on 29, would that be correct?
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Wednesday, June 25th, 2025 AT 5:02 PM
Tiny
STEVE W.
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Yes, should be a dark gray wire. Now you just need to find the same wire under the hood. They don't show any connectors so it should have been a solid wire from pin 20 out to the connector.
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Thursday, June 26th, 2025 AT 7:52 PM
Tiny
BRODYWINTERS1005
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  • 11 POSTS
I never found the end of the wire but could I make a split in the wire and hook a another wire to it and then attach it to the alternator or how would I test the voltage to make sure it's the right wire so I don't mess anything up.
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Thursday, July 3rd, 2025 AT 8:48 PM
Tiny
STEVE W.
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Yes you could splice a wire in for testing. Just be sure it is the gray wire in pin 29 in connector 2 on the ECM. Splice into it and just touch it to the field terminal. Put a meter on the battery and watch as you touch it, if the voltage jumps up and shows it is charging you have the repair, just make it more permanent.
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Friday, July 4th, 2025 AT 7:56 AM
Tiny
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Okay thank you
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Friday, July 4th, 2025 AT 11:16 AM
Tiny
BRODYWINTERS1005
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Can I attach a picture of the connector and the numbers on the alternator so I know where I need to attach the wires to the alternator
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Friday, July 4th, 2025 AT 11:24 AM
Tiny
STEVE W.
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Look in the first reply and you will see the connector you have and which wire goes to which pin. Now hold the plug up against the alternator and look at the wiring diagram for which color goes to which terminal.
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Friday, July 4th, 2025 AT 5:52 PM
Tiny
BRODYWINTERS1005
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I looked at it my plug wires are the other way around mine starts at a, b, c the diagram starts at b, c, d
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Friday, July 4th, 2025 AT 6:14 PM
Tiny
STEVE W.
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It can be re-pinned. Use a thin needle to release the retainer that is inside the connector and just move the pin to the other location. Then look on the alt. And you can see the letters on the socket. P - L - F - S Yours doesn't use the P terminal. But L=B and Red wire, Then F=C and Gray wire and S=D and Orange wire. Usually those pigtails come with 4 connections and you just use the ones you need, not sure why yours only has the three, but you can just move the one to the other spot and make it work.
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Saturday, July 5th, 2025 AT 12:56 AM
Tiny
BRODYWINTERS1005
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It still didn't work I don't know what else to do
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Sunday, July 6th, 2025 AT 6:22 PM
Tiny
STEVE W.
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Are you sure the alternator is good? I've had more than one new one bad right out of the box.
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Sunday, July 6th, 2025 AT 6:27 PM
Tiny
BRODYWINTERS1005
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I just got it not that long ago how do I test it
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Sunday, July 6th, 2025 AT 6:59 PM
Tiny
STEVE W.
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I would take it to a store or shop and have them test it. They will have a machine that can cycle it to test it. There are no real tests other than voltage output with it working on the car, you already know it doesn't charge on your car, if it works on the bench then you would know to dig into your car more.
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Sunday, July 6th, 2025 AT 8:28 PM

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