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cavette
10-07-2023, 06:27 PM
I measured my car's voltages with a multimeter.

1) Battery voltage w/ car ignition off: 12.55v

2) Battery voltage w/ car engine running: 12.45v

3) Battery voltage w/ car engine running and headlights and ac fan ON: 12.05v

4) Car engine running and voltage output directly at the alternator itself: 12.45v

Is this a sign of a bad alternator and must it be replaced? Or should a bad alternator displace an even lower voltage than 12.45v?

Thanks
3ZHP
10-08-2023, 08:30 AM
The battery needs to be at 12.5 so, you need more to charge it. A good alternator will be charging at 14.5. You need to check at the jumper leads (back passengers side) while running. That voltage need to be more than 12.5 to charge the battery.

I just replaced one that was only charging 10.5 volts.

Note: ZHP’s came with two different alternators.


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cavette
10-08-2023, 02:29 PM
You need to check at the jumper leads (back passengers side) while running. That voltage need to be more than 12.5 to charge the battery.

What is the jumper leads at the back passenger's side? I have corrected my original post above with clearer descriptions of the car's engine running.
YoitsTmac
10-09-2023, 07:25 AM
The battery needs to be at 12.5 so, you need more to charge it. A good alternator will be charging at 14.5. You need to check at the jumper leads (back passengers side) while running. That voltage need to be more than 12.5 to charge the battery.

I just replaced one that was only charging 10.5 volts.

Note: ZHP’s came with two different alternators.


Sent from my iPhone 15 Pro using Tapatalk

Is that the voltage you get from your car? I get 13.9-14.0 over two alternators according to my radar detector.
cavette
10-09-2023, 01:29 PM
Is that the voltage you get from your car? I get 13.9-14.0 over two alternators according to my radar detector.

YoitsTmac, wow, we need to meet up as I am in the Bay Area now.
3ZHP
10-10-2023, 07:01 AM
What is the jumper leads at the back passenger's side? I have corrected my original post above with clearer descriptions of the car's engine running.

These! You should get 12.5 volts, with the car off and 14.5 volts, with it running at idle

https://uploads.tapatalk-cdn.com/20231010/a58c54e4e38ca67427810f1bcb8bd5d5.jpg


https://uploads.tapatalk-cdn.com/20231010/6573760967a9559060d12ca5330de769.jpg


Sent from my iPhone 15 Pro using Tapatalk
YoitsTmac
10-10-2023, 07:31 AM
YoitsTmac, wow, we need to meet up as I am in the Bay Area now.

Shoot me a message on instagram! I normally go to BMW CCA meets in the north bay. You just missed an awesome drive this weekend!