I have a bmw e90 320d 2005, pre LCI. Since few weeks I noticed flickering interior lights (normal light not LED), when the car is running, when I turn off the engine they are working normal. The car also displays and ABS module error for over voltage (sometimes popups up when revving the car). I've searched on the internet and decided to change few things: voltage regulator of the alternator (i have replaced the brushes), no change. I have replaced the entire alternator (it has voltage regulator attached to it), everything seemed okay, but then the ABS light cam back on again. I did another research and there was a person complaning with similar issues, and he said that it was loose negative conector to thebattery, so I have decided to tighten it up, since I could easily remove it from the connection without loosing it.
Since then there hasn't been ABS warning for overvoltage, but I noticed today that the interior lights are flickering again. So I have decided to check on the voltage. Here are the measurements I've done:
- Car battery when starting the car: voltage drops to around 11V and gets back up to around 14-15 Volts
- The interior lights when the car engine is not working are around 11.4 volts, and when the car is running they drop to around 10 volts
- The lighter stays around 15.2 volts when the engine is running and drops to around 12 volts with the car engine off.
- The measurements are when the lights are not flickering, couldn't measure that since thay rarely flicker.
My car doesn't have an IBS sensor, so I guess it is okay to charge it at around the same rate.
So my question is, could it be a lose connection that makes the lights flicerking, why would lighter stay at around 15 volts, is that okay? Is it okay to charge the battery at 15.2 volts ? Could it be that there is low voltage that causes the flickering, shouldn't the light be just dimmer and not flickering? Is there any measurement I can do to check further?