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View Full Version : e39: What is happening to my car??



snocohn118
12-14-2013, 02:25 PM
Hey guys,
A few weeks ago I flew home from college in Charleston, SC for Thanksgiving. I drove my 2003 e39 540i M-Sport back and forth from friends houses for the first two days and the car drove perfectly. Then on the 3rd day I got in the car to go to the store and on the way I noticed the radio wouldn't turn on. A few hours after I got home I went to go out again and when i turned on the car it beeped with the reading "Check back-up light." My right back-up tail light was out. The next day the car was dead! I took the battery out and charged it on my Dad's battery charger for about 8-10 hours. I put it back in and the car started up fine. I drove it around fine with the radio working. Then the radio wouldn't turn on again. I had to fly back to Charleston for 11 days for finals and put the car in the garage thinking it would die. 11 days later I went into the garage and unlocked the car. It wasn't dead! I started the car fine and drove it around however the back-up light is out and the radio still won't work. I don't understand what the F*ck is happening. Why didn't it die? Is it safe to drive? I think there might be a short somewhere where its all connected? Im not educated on the electrical system of a car but i just want it to be perfect again. Please help :help

Silverlight
12-14-2013, 02:36 PM
you might get some better luck posting in the e39 section of the forums, but sounds like to me your alternator might be going. When the battery or alternator fails in these cars, the electrical gremlins come out

SmokemhontaS
12-15-2013, 04:02 AM
I was gonna say you might have to plug the code in for your radio but it's an e39 and I have no clue about there radios.

E37
12-15-2013, 09:49 AM
Sounds like your alternator is going out, but why not take the car to autozone for a free OBD scanner use to check the fault codes?

kura
12-15-2013, 12:06 PM
Ditto with some guys above in checking your alternator. Have the car running and see if the battery actually has more than 12V charge when it is running, If not, then the alternator is not doing its charging job properly and need to be replaced.

arbuckle
12-15-2013, 01:53 PM
My advice is not to throw a new battery or a new alternator at your problem until you have them tested. Also, you may want to search the forum for FSU. I had a similar problem to yours and a new FSU fixed it (cost ~$45).

A very easy diagnostic is to an open circuit voltage test. Per the Bently Manual:

Turn your engine off
Turn your headlights on for 1 minute
Read your voltage across your battery.
It should read 12.6 V or more for a fully charged battery.
11.7 V or less indicates a fully discharged battery.

Good luck.