2000 M Coupe will not turn on HELP!

[///Mpmp1025]

After searching the faq, forums and google I was unable to find a solution to my issue. I tried all different search terms and I found nothing that was resembling of the issue I am having.

Yesterday I went to run an errand and my car would not turn on. Earlier in the day I was able to unlock all the doors, the car was getting power to all the electrical systems. A few hours later the locks were not working (I was only able to open the door my key was in), the interior lights did not come on, the car would not start and nothing was being powered. I checked the battery with a multimeter and it had a charge just below 12 volts. To be sure it wasn't a dead battery, I took it out of the car this morning and put it on a battery tender to charge; it was charged, the battery tender switched to storage mode in a matter of 1-2 minutes. All the battery cables are in good shape, no corrosion on the terminals and no loose connections. I left the battery disconnected for a short while hoping it would reset the system, that did not work. I checked all the fuses (mainly #31 and #45, iirc) and they were not blown. I did not remove every fuse in the box, but none were visibly blown (I only have a few fuses that need to be removed to be checked). Now I'm stuck, I've exhausted all simple solutions. Any ideas on what could be causing this? and how to fix it? Please help, I am stuck.

Thank you guys for taking the time to help me out in advanced

The short version: car was working in the morning, a few hours later the car was not getting power. The battery is fully charged but not feeding power to the rest of the car.

-Dave

[Muzz258]

With your multi-meter, check for voltage at the positive jump start terminal under the bonnet/hood. If there is no power, then check the crash disconnect in the positive lead by the battery for corrosion etc. If there is power there, pull out the wiring diagram for the car and keep tracing the voltage until it stops.

[328 Power 04]

At under 12V, the battery is not fully charged, it's dead. The tender is just misleading you. Replace your battery, or at least try a jump.

[///Mpmp1025]

This ended up being a dying/dead alternator. I had it rebuilt locally at a shop. Thank you guys for the help.