W220 Battery Drain 1.1A

[JammyBob]

I have recently bought a W220 and it has now started with the dreaded battery drain. I have tried pulling all the fuses from the three fuse boxes as well as testing the mV on each fuse when the battery is in sleep mode and the voltage is zero as it should be.

With a multimeter inline I am getting 1.0-1.1 amps pulling constantly after about 5 minutes (tested up to 40 minutes) I'm thinking it could maybe be the alarm siren, voltage regulator or something with the alternator.

Just testing it unlocked now with fuse f58 removed for keyless go to see if that has any change. Any help would be greatly appreciated.

Thanks

 

[mersum1es]

most common culprits: Comand system, memory seats...
voltage regulator fault is quite rare but easy to test; just remove wire from alternator
unfortunately s-class is so full of electrical stuff its hard to tell which device is left on and keep BUS awake... even with SDS it could be a PITA

 

[MWCLS]

As OP says.. I think they only way you will get to the bottom of it is Star diagnostics or the like. Good luck.

 

[JammyBob]

@mersum1es Would pulling fuses stop those issues?

@MWCLS thanks I hope I can get it sorted, put a good few hours of my own testing into it so far.

 

[m2287]

This can take a long time to rectify but as mentioned above, command, memory seats, alarm also the PSE pump have been known to cause drain... I’d remove the fuses for these and see if there is any improvement

 

[JammyBob]

Thanks m2287, I will retry doing just those fuses to see if that has any effect I did them all in big batches but I don't know if that would have made the current draw still stay high