x5 lost all electrical power.. Help!!
 

I was on my home from work with the family in tow and my baby (my 2001 4.4 x5) just completely went dead. all of the lights and everything was dead. Since I had no hazards i had to get out the car and direct traffic around my disabled vehicle until someone came to help me. While waiting for a friend to arrive the lights and everything came back on after sitting there for awhile 10-20 mins . I thought that was weired but i needed to get the family home so I got in the car and started driving home luckily i was less than two miles away. On the way home the car cut out for a second but when i tapped the breaks it seemed to come back.. not sure what happened.

When I got home I decided to check the battery and maybe alternator by looking at the voltage. After the getting the family into the house i went back outside and the truck was totally dead again. SO I manually open the rear trunk to get to the battery. Midway through taking off the bolts the truck came back alive.

I checked the Battery and it was between 12.-12.9 volts

When I started the truck i read 13~ volts.

SO that being said I am not sure where to start to find the problem.
Could the alternator be bad? over heating , voltage regulator?. I just replaced the alternator 02/10, but i was seeing the voltage increase when started.

Any help or ideas would be very much appreciated. Thank you in advanced!

Sounds like you have a loose connection. As its all the power going off at once I'd say it's one of the battery cables at either the battery end or the engine bay end.

I guess i will start at the boot and then check the wires in the engine bay. Could this be a fuse or something...

I recently had my Transmission repaired/replaced. could the removal process / installation damage some cables?

Won't be a fuse. If it was a fuse the power would just stay off and I'm pretty sure you're not leaking power because you have power then you don't. Check all major lead connections. Remove them and clean them off if need be and then re-connect them.

I would assume they would disconnect the battery for the tranny repair so most likely they've just failed to tighten up a connection

Hold up. So with previous cars, the way I would test if the alternator was working, is disconnect the battery while the car was running.

Does this not work on BMW? Will the alternator not keep the car powered if the battery connection was loose?

DO NOT DISCONNECT THE BATTERY WHILE THE VEHICLE IS RUNNING UNDER ANY CIRCUMSTANCES!!!

How old is your battery?

I think the battery is about 3 yrs old. A die hard I picked up from Sears.

Paul1994,

Battery might be failing. Also, nominal voltage at the battery terminals @ 1k RPM should be 14.4 to 14.6 VDc. Alternator failure after a known good replacement seems unlikely.
Have a "real" (load) test done on your battery at a Autozone or similar.

I will try to do that tonight..

Would a bad battery cause complete Failure of all electronics in the truck though?

I just thought that was weird.

I dont think it's the battery or alternator, as you have zero power one minute then full power the next. As already said I would be checking the main battery connections, sounds as if something is loose somewhere.

Lets us know how you get on.
Dweeb