Charles Morgan
MB Enthusiast
- Joined
- Feb 2, 2010
- Messages
- 8,206
- Car
- Mercedes 250CE W114, Alfa Romeo GT Coupe 3.2 V6
My BMW M535i has always had issues with batteries - regularly flat and in need of replacement. On one occasion the car was stuck in heavy traffic on the M40 after an accident and it died - the garage decided it was a faulty alternator and changed it. Recently I've been prepping it ready for sale and have been out and about a lot, sometimes in heavy traffic, and the battery has been playing up. The other day the engine died at idle and the battery was as flat as a pancake.
Having replaced the battery I thought I'd check alternator function. Battery was showing 12.6v in the car then when the engine was started the voltage across the battery was down to 12v when it should have been 14v or so.
Revving the engine hard then letting it slip back to idle at the voltage was then 14.6v attenuating to about 14.3v after several minutes and remaining at that level.
What could be causing this? The alternator is new as is the battery.
Having replaced the battery I thought I'd check alternator function. Battery was showing 12.6v in the car then when the engine was started the voltage across the battery was down to 12v when it should have been 14v or so.
Revving the engine hard then letting it slip back to idle at the voltage was then 14.6v attenuating to about 14.3v after several minutes and remaining at that level.
What could be causing this? The alternator is new as is the battery.