W220 s320cdi Starting ProblemHe
Bit hard and yesterday doesen't start at all, When I swich the key in position II
the light from instrument cluster are turning off and I can't turn on the navigation, AC, etc. And in this night I can't open the car from the key, I can Close and open the car only With physical key, but When I press the Button to open the hazard lights and headlight still works, even the alarm. What's the problem? It's supposed to be the battery? I tested the battery When the Merc doesen't star first time and it was 9.8V.


The best approach is to disconnect the negative battery cable, fully charge the battery with a good charger, then test the battery.
You also need to clean both battery terminals and carefully inspect the serpentine belt and its tensioner.
Check the battery voltage after charging, and hook everything back up. Then see if the car starts. If so, check the voltage at the battery with the engine running - you should have 13.6 - 14.2 vdc.
If the charging voltage is within spec, and everything else looks good, but the battery voltage gets low again (with less than a week of sitting), it is probably time for a new battery. The W220 needs a very good, high-amperage battery.



