[carlfxy]

Hi,
2010 bmw 328i, a couple of times now the lights dont come on when I open the car door. No dome lights no dash lights, as if there is no battery in the car. Put the key fob in, nothing doesnt click into place. No response or life. Checked voltage at jump posts, came back fine at 12.7v. Tried jumping anyway same deal.

Tried turning on lights etc nothing works. A couple of hours later, everythings fine. Works like normal.

What can cause this ?

Have a new battery in there, the positive terminal blow off cable is a coroded from overcharging the old battery when it was dying. So ive ordered a new one of those and throwing it in.

THe ibs is disconnected, the battery is unregustered. I just dont get it and am unsure how to diagnose it. Was thinking it was a loose positive cable on the battery cause its somewhat coroded but why no start or life when jumpers on, and the voltage reades fine on the jumping posts... what am i missing here

[gbalthrop]

Originally Posted by carlfxy

... 2010 bmw 328i... when I open the car door. No dome lights no dash lights, as if there is no battery in the car.
Put the key fob in, nothing doesnt click into place. No response or life. Checked voltage at jump posts, came back fine at 12.7v...
What can cause this ? ... what am i missing here

The 328i has THREE B+ Cables from Battery to different Components:
1) Large B+ Cable from (+) terminal of Battery, via Battery BST to Jumpstart Terminal under hood. If you have 12.7V
at Jumpstart Terminal, that Cable, its connections, and your Battery are all Good.

2) Medium B+ Cable from Inboard side of Rear Power Distribution Panel (RPDP) on top of Battery to X13020 connector
on Right Side of JB Fuse Panel. THAT is where your issue lies. Either due to a loose 13mm nut holding cable to RPDP,
or a loose connection at X13020. See attached Photo of B+ Cables from my 3/2007 build 328xi. Check 13mm nut under
"Flip-up" cover labeled at bottom of photo.

3) Small B+ cable to VVT Relay in E-box, as shown in photo just above #2 Cable. Clips into rear of RPDP, and is probably OK.

An intermittent loss of Power is almost ALWAYS caused by a loose connection. ALL your fuses for CAS Module,
& FRM (lighting), are on JB Fuse Panel, so if JB is NOT getting voltage, NOTHING lights up and Key Insert fails.
George

[carlfxy]

Thanks George exactly what I needed to know, appreciate it. Ironically I'm replacing the Large B+ cable which clearly isnt the issue. Your image and description has solved my problem and concerns... THANKS

I did just check the recalls on my car and saw i have this one outstanding .....

https://www.e90post.com/forums/showthread.php?t=804545

The connector for the positive battery cable connector and the corresponding terminal on the fuse box may degrade over time. Over time, the high current flow and heat from electrical resistance may lead to a breakage of the connection, and a loss of electrical power to the vehicle.