Battery light/alternator instrument gauge

[kchase731]

Hi everyone.

I'm rather new to the e30 scene and just experienced my first major issue. The car died on me while driving it the other day, I tested the battery charged it up car started just fine again so I figured it was the alternator. That was a pretty easy swap. Afterward I started it right up and drove a round a bit the car stranded me again. I started reading in the forums and it looks like it could have been the battery light. I opened up the dash and replaced it, but it's still not coming on when I turn the key, to make things even more bizarre it comes on real briefly when I shut the car off. I do not see any evidence of issues with the soldiers on the cluster board. That said my tach light started acting up, when I turn the lights on the tach light wasn't coming on but if I tap the gauges it comes right on, it's not the bulb.

Currently the car is not charging the battery at all, so there definitely something still wrong. Any help is much appreciated.

Video of the gauge behavior.

https://youtu.be/52Ecxa5bLHc

[ecsk]

Something very wrong with your cluster, that could cause the alternator won't charge the battery.
If I were you I'd find another cluster to try.

[ba114]

what year is it?
Late model clusters have a resistor wired in to prevent the "no charging battery light out" issue.

[reelizmpro]

That's a late model cluster. Battery light should be on with key on. You should have a bypass resistor in parallel with the batt bulb. Bmw updated this in late 85. The green LED's should not be on with the car running. Try another cluster to help troubleshoot.

[kchase731]

It's an 89. I just purchased a cluster board, that's been remanufactured. The gauges and everything all work so I'm hoping I can swap the board and it will be ok.

Does anyone think I also need to change the Si board?


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[ecsk]

Does anyone think I also need to change the Si board?


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Swap the cluster board to test it first, if everything work why change more part. SI board is not cheap.

[kchase731]

New si board new cluster board still nothing. Does anyone know how to test the voltage at the alternator while it's running?


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[dnguyen1963]

New si board new cluster board still nothing. Does anyone know how to test the voltage at the alternator while it's running?


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Place a volt meter anywhere in the system (cigarette socket is a good one) and check to make sure that the alternator can put out at least 13.6 V.

[kchase731]

I'm definitely not getting 13.6 v at the battery or at any other electronics which is why I wanted to test it at the alternator. I'm just not sure of a safe way to check the voltage at the alternator while the car is running


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[dnguyen1963]

It's the amperage that kills you, not the voltage. Sticking the meter into the cigarette socket while the car is running won't kill you. You can test at the alternator if you want...positive goes to the post for the big red cable and negative goes to the chassis.

[kchase731]

So I'm getting 0 at the alternator. I checked the voltage regulator and the brushes are long and new. It's a new alternator and the belt is definitely tight and spinning it so bad alternator?


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[dnguyen1963]

Yeah, it does sound like your alternator is dead and you are running off your battery.

[reelizmpro]

Have you checked the wiring harness to the alternator? You got the correct alternator with solid mounts right? Assuming you have a 325i. Take a pic of the alternator.

[THMotorsports]

If you leave the car idling, does it shut off within a few minutes and then the batter is completely dead? If so, that could be a telling sign of alternator failure. Agreed with the guys about putting the volt meter into the cigarette socket to get a reading. If that concerns you, then you could put the meter on the terminals and have someone else (a helper of sorts) turn on the air conditioner, light, etc. You should see a spike in voltage once these things are turned on and then the voltage settle back down around 12V.

[wilholl]

So I'm getting 0 at the alternator. I checked the voltage regulator and the brushes are long and new. It's a new alternator and the belt is definitely tight and spinning it so bad alternator?


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As in "0 Volts" at the alternator terminal?
If this is true than your alternator is not connected to your electrical system.
You should be able to measure at least battery voltage at the output terminal.