2002 540i. Was running fine for the last week, recent changes were new SLS air pump, oil change and brake fluid flush. this happened about 3 days after the fluids.
Went to inlaws' house, when leaving I went to start the car and heard a slight bang (could have been the starter engaging). Now when the key is in any position besides off, some of the dash lights flash rapidly and you can hear a few relays going. When you turn the key back off, the interior lights slowly pulse off and on, like on a 5 second cycle.
Starting to pull fuses and check them now...with the weird light thing I am wondering if a module died....
battery is showing 12.3v, even tried with a nice plug in jumper/charger.
I've been getting teh battery light flickering for a while, I assumed the alternator was on its way out.
check the trunk wiring harness? but fuses should be blowing in that case... flickering battery light may also be your oil level sensor. They are on the same circuit in my 97 540.
LOL ended up being battery. I guess it would hold a charge but couldn't put out any amps? I couldn't even jump the car. New battery and everything is working 100%. Alt seems to be putting out good voltage still too. Just an update for someone googling this issue 5 years from now...
Thanks for the feedback. 12.3 V indicates that the battery is only 50% charged. The plates were probably sulfated, so it could not deliver much current. Once the battery is sulfated, it becomes non-serviceable, and should be replaced.
Last edited by edjack; 07-12-2020 at 07:49 PM.
Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.
Wrong..... you desulfate a sulfated battery with a capable slow charger, usually takes 48 hours or more. Best way is to drain some of the old acid out, refill with distilled water and the slow charge breaks up the sulfur build up off of the cells, hence, desulfation of the cells. You don’t hit it with high Voltages.
Set the controls for the heart of the sun
yes u need to do it slow but slow means low ampere, not low voltage. you need to use a charger that can charge with higher voltage. this process is also called as equalization process.
https://batteryuniversity.com/learn/...alizing_charge
Last edited by TiesTorN; 07-14-2020 at 09:53 AM.
^_almost nobody here has a charger that will do that.
A good smart charger is all you need to desulfate the lead plates.
Sigh, didn’t need to read it, my slow Genius chargers all do it, and do it well.
Set the controls for the heart of the sun
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