New alternator and battery, still low voltage

[Phoenix LSX]

I've been having some issues out of my '05 325ci 5 speed convertible. The battery keeps dying on me. I've tried different tests but no luck. This morning, I bought a new alternator and battery, and installed them both at the same time. Somehow, I'm still only getting 11.9 volts at idle and it slowly drops as I drive around for about 30 minutes. Any ideas? This is my 4th alternator in 2 weeks.

[X3456]

There's a loose connection somewhere drawing more power then it should be...what about that roof...when was the last time you used it?

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[Phoenix LSX]

Earlier today. Right after replacing the two, I let it idle for a few minutes, checking the voltage. Afterwards, I put the top down and went for a drive around town to see if the voltage drops and it does.

[nonturbodan]

What kind of alternator are you putting in?

[harrier]

4th alternator!? There is a story here.

You shouldn't need to replace the alternator most of the time, but you should get a new, oe voltage regulator. Are you getting alternators from junkyard?

Measure the alternator output at the alternator while the engine is running. Also measure voltage at the studs in the engine bay. It is also possible you have a bad battery or loose connection. Battery clamps are notoriously oversized.

[jclausen]

Do yourself a favor take the car to a BMW independent shop for the correct diagnostic

[randy72877]

Check the positive jump start point under the hood. Take it apart and make sure the connection is clean and tight. This is the junction between the main battery cable and the cable that goes to the starter and alternator.

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[X3456]

I'm not saying this is your problem but randy #7 is right ! it should be a legitimate concern...I had this problem and it took me a couple of weeks and a couple of early mourning trips to the car only to find out the battery was dead...
https://www.bimmerfest.com/forums/sh...php?p=12875513

04 went down

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[Phoenix LSX]

I was using Carquest brands, now I have a new Bosch. Here's another thing. The battery only drains when the engine is running/key on. If it's off, then the battery will go back up to 12.5 after sitting for an hour or so.

[X3456]

all connections to and from the alternator secure!?

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[Phoenix LSX]

Yes. Everything appears to be secure. I tested the voltage at the alternator, showing around 14 volts.

[vinyldude]

My guess is something is drawing unexpected amounts of current, and it does not happen when ignition is off (or when the car is in "sleep mode").
You could try pulling out fuses, one at the time, in an attempt to find where the problem is. Probable culprits could be for instance electric motors, which upon failure easily leave themselves in near shorted condition. Check anything behind the high current fuses, and for instance the secondary radiator cooling fan.

[X3456]

I want to go back to the start, you have installed not only a new alternator but a new battery correct? Why? we're you having this problem before hand?
Most importantly...
are these two components correct in spect. other words are they components that came with the car from the factory?
Finally, (I couldn't resist) have you installed an aftermarket radio, speakers ect....

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[Phoenix LSX]

All fuses are good.
When I bought the car, it was perfect.. for a week. That's when I started noticing issues.
Alternator and battery are of correct spec.
Previous owner had subs installed but removed them. Stereo is still factory.

[X3456]

Ok...Ok... you've forced me to.bring out the big guns:
https://youtu.be/L1T7u70rog0


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[Phoenix LSX]

So I took it to a Euro garage yesterday. They told me the red cable from the alternator goes to a stud on the starter and that stud has come loose. They tried to tighten it but couldn't and recommend a new starter.

[tsughibughi]

So I took it to a Euro garage yesterday. They told me the red cable from the alternator goes to a stud on the starter and that stud has come loose. They tried to tighten it but couldn't and recommend a new starter.

So did you fixed it?

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[Liquidity]

So I took it to a Euro garage yesterday. They told me the red cable from the alternator goes to a stud on the starter and that stud has come loose. They tried to tighten it but couldn't and recommend a new starter.

Time to find a new shop. Starter has nothing to do with low voltage.

[shogun]

Also check the ground cables, especially the one from engine to chassis. Yesterday I fixed an E32 which did not start, sounded like the battery is empty, just a few cranks and then stopped, then the starter only clicked, turned out the ground cable from engine to chassis was completely corroded and oxidized. Replaced that one against a new cable and engine started immy and starter turned as it should. Bad engine grounds may be caused by loose, rusted or damaged ground terminals or wires. A loose, damaged or corroded ground battery. Bad ground could cause an engine to not start. This is one of the more obvious signs of a bad ground, the same way as a loose battery cable or a dead battery.
Bad ground cables are a major problem on our older cars, always check them and replace.

[randy72877]

A quick way to test if the ground is bad between the engine and chassis is to connect jumper cables to the NEGATIVE jump start point and the other end to the engine. Or just measure voltage drop from the engine to chassis with a multimeter.

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