This is pretty obviously an electrical problem, which unfortunately is not my forte. This morning I went to start my 95 M6, and had no power at all. No lights or anything. This has happened before, but the last time I had this issue was in the fall right before it went into storage. It was fairly frequent before then though, so it's pretty erratic. Here's how it typically goes:

1. Unlock vehicle using the key fob and alarm (dealer installed and not some hack job) disarms
2. Lights come on when I open the door and everything behaves normally.
3. I put the key in the ignition and try to turn it over. Sometimes the dash wakes up and flashes when I try to crank it, other times nothing comes on.
4. I'll go and fiddle with the negative battery terminal and the vehicle regains power and the alarm goes off, as it should.
5. From here on, it's just rinse and repeat steps 3 and 4 until it starts, or I just get annoyed and hop in the DD. Jumping the battery doesn't help at all.

The battery connections are clean, and it's never seen salt or snow so corrosion on other connections is very minimal. I have no idea why this happens. The last time I drove it before this happens can be an hour or a week, so it doesn't seem like it's an extraneous battery drain problem, and the voltage is fine when the dash lights work.

Any thoughts?

 

Sounds like you are right on top of it. Bad battery connections. Make sure the tabs on the cable rings are making contact to the lead terminals on the battery. They have a tendency to get flattened out (the bolt can seem tight, but good contact is not there). Don't overtighten and ruin your battery.

 

Also, may not be a bad idea to use a small wire brush on both the battery and the tabs on the cable rings. May not look corroded, but still have a glazing on the surface preventing a good connection.

Check the cables for swelling or cracks from internal cable corrosion.

Also wouldn't be a bad idea to clean all the grounds you see as well as the positive contact connector on the fender 6" from the battery.

Wouldn't hurt to make sure the wire connectors are tight and not corroded at the starter as well. But I would be leaning more towards battery, cables, grounds.

 

A mixture of baking soda and water slathered on the bare terminals and cable ends using a toothbrush, will help remove the corrosion, particularly the sulfates that form from the battery gassing.

 

I have a terminal brush, and I'm pretty sure I've cleaned them since this started. Doesn't hurt to try again though. It's just so bizzare, because I can have full power, and go to crank the ignition and lose 100% of my power. When I got home from work today I tried to lock and unlock it using the remote, and the alarm chirp when I pushed the lock button was really weak, low pitched, and carried on until I opened the door. It sounds like it's getting power but only a tiny bit. I also noticed that my fuel gauge is still reading even though there appears to be no power going to anything. All other gauges are just resting on their stops like they should be. I'll try cleaning the terminals and see what that does.

 

I think I got it. Pulled apart all the post connections that are around the battery and, using one of my dremel bits and my drill, brushed the crap off of them. Did the same for the battery connections, and discovered that the threads on the negative post were pretty torn up. So I replaced the posts, put dielectric on everything and reassembled. It's working fine now. It seems like the post wasn't threading in all the way, so that would definitely explain it. Probably didn't need to make this thread to figure it out, but thanks for the help guys.