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Battery charging red warning light came on

Discuss problems you have had or are having with your Z4
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ph001
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Battery charging red warning light came on

Post by ph001 » Mon Nov 20, 2017 12:01 pm

I’m not quite sure why everyone here was diagnosing battery??? Usually, the red light is alternator charging voltage that is low. You need to put a voltmeter on the battery with the engine running. Anything under 13.5V is an alternator issue.
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Chris1981
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Battery charging red warning light came on

Post by Chris1981 » Mon Nov 20, 2017 2:01 pm

ph001 wrote: Mon Nov 20, 2017 12:01 pm I’m not quite sure why everyone here was diagnosing battery??? Usually, the red light is alternator charging voltage that is low. You need to put a voltmeter on the battery with the engine running. Anything under 13.5V is an alternator issue.
Exactly right... if it were the battery your car would not start! I had red battery light on my old E46 and it was alternator, the battery was fine!
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cj10jeeper
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Battery charging red warning light came on

Post by cj10jeeper » Mon Nov 20, 2017 4:30 pm

This is a resurrection of a dead thread. Most recent post is observing a good voltage from the alternator, so that's not the fault
The battery is dead if it shows 11.5v and not holding a correct charge and needs replacing immediately. Only caveat is this is assuming the voltage is back to 11.5 a short time after parking and your not talking about left standing for a week or so.
Left overnight it should be at least 12.x, ideally 12.4 - 12.6v on a healthy battery

Although a very low voltage might start a car, pretty soon it won’t and you'll start to get all sorts of electronic errors...
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Battery charging red warning light came on

Post by bowler » Mon Nov 20, 2017 5:01 pm

Interesting post, describes what mine is doing perfectly!

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Battery charging red warning light came on

Post by Bertz4 » Wed Nov 22, 2017 8:32 pm

Just to add another element for interest, my son had the charge light on on his E46 330D, battery volts 12.6 engine off after charging, running about 12.3. Changed alternator still the same?? Got old alternator checked on test rig and was fine. Much head scratching, then noticed the auxiliary belt did not seem to speed up when rev’d, paint mark on belt confirmed. Turned out the rubber torsional damping element in crankshaft pulley had failed. Not sure whether the Z has a damped pulley, but it’s an interesting story.
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