Hello,

I would like to ask regarding my battery's voltage. (I can check the actual voltage thru the on board diagnostics of the A/C controls of the W210)

From idling, the reading is about 12.2 volts to about 12.7 volts during revs (does this mean my alternator is OK?)

But upon closing the engine and reading the battery's voltage, it just reads to about 11.2 volts to 11 volts. But this can still start the car without a problem.

My question is:
Does the battery have to be at the 12 Volt range? or is 11 Volts normal? Or there is something wrong with my battery?

Thank You for your help.

 

Thanks for that.

So I assume my alternator is almost broken?

There was a time when the car did not start when it was left un-used for about 3 days. The voltage was around 9 volts only.

Is there a chance the battery is the culprit too?

 

Your voltage is higher with engine running but not a normal value. It seems like bad commutator brushes in your alternator (usually replaceable part). Otherwise voltage would drop even lower then before starting your engine.
Your battery looks good and strong but you have to charge it with regular automotive battery charger to bring it upto normal state of charge. Even new alternator will not fully recharge it at this point.

 

My ml350 2006 is running between 13.7-13.9 but is off with 12.4 . Just replaced battery after no start without a jump . Now it still has red battery visit workshop almost always on but still runs at 13.7-13.9

any thoughts ? 💭

😊