So...New Years eve, I get to my friends house. Mini seemed to be a little slow to roll the windows down, but I marked it up to it being in the mid 20s.
Fast forward to the hung over next day, and she wont start.
I figured battery, obviously, as cold can kill them a bit...that and our cars are often finicky when they dont have exactly what they need in the voltage department.
Charge it at 20 amps for about 45 minutes, and still nothing. Battery was reading 12.7volts. Bumped it up to 40amps of charge, and she fires right up.
After driving it home, I figured I would go ahead and replace the battery...it could have been a dead cell, and that means not enough juice to get the starter going.
The new battery did not work. It still wont start.
Next was the starter, which starts the car when it has a charger pushing 40 amps to the battery, but not with the battery by itself. Starter tested fine at the local autoparts store, and it looks fine on the inside as far as brushes go.
We did notice that after getting it running, the battery went from 12.7v to 12.3 in almost exactly 3 minutes time...which makes me think alternator. But a bad alternator wont cause the car not to start, would it?
Also, my buddy has a VAG-COM from a few other BMW builds he has done, and it would not connect to the engine...but the DME has to be fine, as it runs like a 2007 MCS with 70k miles should when we get it running.

Any help with this would be greatly appreciated. I just tore the engine bay apart again to check the starter a second time (it only took 30 minutes this time, not 4 hours), and I am kinda getting tired of seeing its nether regions every weekend.

 

sounds like a high resistance connection

check all the connections from the plus side of the battery to the starter and then check all the grounds from the battery to the frame and from the engine to the frame

any of the connections could be loose or have corrosion

 

Would you happen to know where these grounds are located? I have gotten pretty intimate with my MCS, but I have never seen a wire and thought, "Oh, thats a ground".
I feel like that is actually all that is left for it to be, considering the circumstances.
But like hell if I can find pictures of ground straps in the car to reference...

 

There is a possibility that the issue is the Alternator (I have experienced alternators that remained in a excited state so on start up the excitation field was charged causing a magnetic lock on the alternator and the starter had big issues turning over the engine with the drag of the Magnetic Drag of the alternator) This issue had later be seen again when a performance aluminium pulley was spun on the alternator shaft because the torque compressed metal in the pulley seat.

I would just for self satisfaction pull the alternator and test it...

As for the VAG-COM connector, the 2002-2006 (R52 -2007) the OBCII connector had a bridged connectors 6 and 7, on the 2007 -on the 6 and 7 connectors are not bridged. Because of this, the connector cables are not interchangeable.

Ground strap locations... look here...

https://www.northamericanmotoring.co...ne-ground.html

I hope this info helps...

Motor on!