What did you do for your ZHP/BMW today?

Battery would be my first guess.

Sent from my kick-A Galaxy S3

I would say alternator. How old is battery?

Sent from Williamsburg, VA USA

Battery is probably OE.

But if it was the battery I would have thought it would be just dead. Not dead after the car was started and running fine and then turned off for 3 seconds.

How do I tell if my alternator is Valeo/Bosch?

I'd start with the battery: it's far easier to pull & have tested (& potentially replace) than the alternator & the E46 is known to act all sorts a fool when it's running on a weak battery.

And yes, I know how a car's electrical system works (battery for starting & alt for engine-on ops) & that my advice is a bit counter-intuitive given the symptoms, but there are far fewer reports of bad alternators than bad batteries. /$0.02


iP5. Tapatalk. Bauce.

Check the output in the battery terminal. Correct me if I'm wrong...at least 14.3 VDC. That is the output of the alternator charging the battery. Anything lower...then the alternator is asking for help.

Dalton,
I'm guessing battery. At idle, you aren't turning enough rpms to really throw a good charge from the alternator over to the battery. All the lights and instruments are using up the lower amperage the alternator is putting out at idle,you've got to rev it up a bit for the amount of amps the alternator is producing to have some extra to charge the battery too.

And this cold spell isn't helping, had to replace the battery on my S10 this morning, it left my son stranded last night. I drove it yesterday and it was fine, he called to tell me it was dead in the parking lot at work and wouldn't jump, I charged my jump start box overnight and couldn't get it started this morning. I dropped a new battery in and everything is fine again.

Thanks for all the help fellas. Got more replies than I had thought.

I'll try to get the battery tested tomorrow and see where I'm at. It seems that with other alternator stories that the red battery light comes up on the dash, and I didn't have that. Hopefully I'll be able to just get a new battery at worst.

mine acted up funny in other ways when the battery was on its way out. I'm gonna bet on your battery too.

As for how to tell the difference between alternators take out your air filter and stick your camera phone behind it and take a pic, it should have markings on the back

I'm guessing battery. :biggrin

Thanks guys. Any recommendations on batteries?