5-Series (E12,E28, E34, E39, E60)Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)
Hey all again, long time no see. Recently my 97 540i has been going through hell. When it starts up, the voltage rapidly fluctuates from 13.8 to 12.0 and back up again. Adding any kind of electronic consumer (lowering windows, headlights, changing from park to drive etc.) will some times kill the car completely as though the key were turned off and then back on. When its not killing the engine, the voltage shift causes my subwoofer to "pop." The alternator was replaced a little more than a year ago and I'm afraid its the problem again. Has anyone else had this issue before or have a possible solution?
I knew it was time to post this problem as I stalled it out in the middle of Michigan Ave. and was sworn at in about 8 different languages.
the battery is perfect. I thought at the beginning that the battery was to blame so I disconnected the battery with the engine going and volts freaking out....still the same deal. Its up to 183,xxx now and still doing pretty well other than this.
Did you replace the alternator last time with a factory part? Have it rebuilt?
If you monitor the voltage while running does it spike all over the place or does it stay constant until you put a load on it then it just cant keep up?
Maybe try checking the ground cable at the battery to the chassis. Take voltage readings at the battery and also at the jumper post under the hood. Make sure you have no voltage drop from 1 to the other.
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