QuestionThe battery indicator light comes on when the car hits 4500+ RPM and goes off when the revs fall below 4000. It may be my imagination, but the car seems slightly sluggish at lower RPM. The car starts well but I'm a little concerned. As is its tradition, BMW is vague when it comes to its owners manuals.
AnswerHi Charlie,
I have checked and found no service bulletin relating to the problem you described. You may be describing 2 separate problems here (charging circuit and engine performance).
I have seen previously where alternator diodes allowed overcharging of the battery which made the battery checklight come on. But you need a battery and charging circuit tester to verify this (not just any cheap battery tester or multitester). In addition, a computer scan would be in order.
The sluggishness you perceive can only be checked via two
methods: verifying it with a test drive, hooking up a good scanner to check for faults if any, and checking the operating parameters of the engine (live data stream with an OBD scanner, and thru diagnosis in a GT1 or DIS).
And yes, BMW manuals do not go into details of car problems,
diagnosis and repairs.
Tino
Tino
