[jonobo]

My 2012 328i has been running great until this morning when it wouldn't turn over. The battery is from BMW and is about 2 years old. I tried jumping it, but that didn't work. I connected the positive to the terminal post in the engine bay.

After that failed I tested the voltages with my multi-meter. The battery shows 12 volts. But the terminal post only shows 3.2 volts. I then pulled the cover off and there are two cables connected. One cable also shows 3.2 volts but the other shows 11.9 volts.

Also, it doesn't seem as if the rest of the car is lacking power...the windows aren't slow, the lights are bright, etc.

I've attached pics of all three readings. Any help will be greatly appreciated.

[jwalker87]

Where were you placing the negative multimeter lead, and was it the same place for both readings?

[Welcome to NBA Jam]

Potential engine ground strap?

[jonobo]

I tried several places including bolts off of the engine, bolts on the engine and castings attached to the engine. That made no difference. For all three photos I used a casting at the front of the engine.

[ryan stewart]

I always use the bare stud coming out of the inside of the fender.

[TunafishE93]

Known problem, known solution.

[Mantraxalos]

Yes, what if you use that bare stud by the fender?
I can't remember exactly, but didn't some people have a loose positive post in the engine bay? Perhaps that wouldn't even lead to this issue though.

[jonobo]

The 3.2 volts was a bit of a red herring. This morning it had dropped to 1.8 volts.

My car was manufactured after the recall mentioned by TunafishE93 but that made me look at that cable more (thanks). I opened my battery tray to discover it was half filled with water. The lug was so corroded it broke off when I pulled the battery out. Luckily, the threads on the bolts are still good so I don't have to replace that long cable, just the short ones to the battery.

New parts ordered...I will be surprised if this doesn't fix it.

[jonobo]

Per dpaul on a different thread, I will be doing some major investigation to find the location of the leak. I will post my findings when I'm finished.

[TunafishE93]

They should really have a drain in there.. I might added a drain myself..

Glad you found it though.

[jonobo]

Wrapping this up...I did the temporary fix of using a new lug while I was waiting for all the parts to arrive. I replaced the four rear light gaskets and the battery cables. My car is running perfectly again.

One note....while replacing the battery safety terminal cable, it wasn't obvious how to pull the igniter connector off. There are quite a few different types of CPA's (Connector Position Assurance) for automotive and I couldn't find any references to this one.

The top of the connector needs to be pulled up (I used a small flat head screw driver) and then the whole connector can be pulled off.

[dez320]

Originally Posted by jonobo

Wrapping this up...I did the temporary fix of using a new lug while I was waiting for all the parts to arrive. I replaced the four rear light gaskets and the battery cables. My car is running perfectly again.

One note....while replacing the battery safety terminal cable, it wasn't obvious how to pull the igniter connector off. There are quite a few different types of CPA's (Connector Position Assurance) for automotive and I couldn't find any references to this one.

The top of the connector needs to be pulled up (I used a small flat head screw driver) and then the whole connector can be pulled off.

Hi, I'm having the same issue on my bmw 320D 2010, can someone please give me more information on how the temporary fix of using a new lug works?

I have also looked in the battery try and all cables look fine - any suggestions on where to look next? Any help is highly appreciated.
Dez