W221 Power Glitches

Discussion in 'Electronics' started by Kay187, May 16, 2017.

  1. Kay187

    Kay187 Member

    Messages:
    55
    Joined:
    Aug 31, 2012
    Location:
    Scotland
    Car:
    S-class 320 CDI
    Hi all,

    Just looking for some advice. I've noticed the electronics going a bit funny in my S class where

    - in the morning the car has a very lazy start which feels like a weak battery
    - the parking sensors go off at times but are fine after a restart
    - climate doesn't kick in properly until car is driven for a bit
    - when car's not driven for a few days remote locking sometimes doesn't work but is fine after a good drive

    I've had codes read (Delphi system and not Star) which were a number of sensors for various components linked to the above but upon clearing nothing has come up. My mechanic is saying it's most likely a weak battery as it can trigger all sorts of codes when there's not enough power to the electronics.

    I'm thinking the same but can there be something draining the battery when it standing? I came across some posts which were hinting this can be the case as well.

    Any advice would be appreciated.
     
  2. zipdip

    zipdip Hardcore MB Enthusiast

    Messages:
    2,499
    Joined:
    Mar 5, 2015
    Location:
    Essex
    Car:
    s320
    Well the W221 is very voltage critical,but as you know there are two batteries,the small one in the engine compartment and the much larger one behind the rear seats in the boot,it would seem you have both batteries playing up,my suggestion is get the alternator checked out Halfords will check the small battery in the engine bay and do a alternator check.
     
    1 person likes this.
  3. OP
    OP
    Kay187

    Kay187 Member

    Messages:
    55
    Joined:
    Aug 31, 2012
    Location:
    Scotland
    Car:
    S-class 320 CDI
    I did check the voltage via the hidden menu and it give 14V when car was running and 11-14v with the car being off so wouldn't that indicate the alternator is ok? Good shout on getting Halfords to do a battery check though, I'll give that a try once I get a chance.
     
    Last edited: May 16, 2017
  4. zipdip

    zipdip Hardcore MB Enthusiast

    Messages:
    2,499
    Joined:
    Mar 5, 2015
    Location:
    Essex
    Car:
    s320
    Would not hurt to make certain the earth leads on the battery and to the body work are tight,you may need to find a merc specialist with star to find the problem,that should show up any problem with the starting battery,the fact you have problems with the other things on the car when it has not been driven for a while is either a battery drain when left or the big battery in the boot is shot,maybe worth removing one of the side panels in the boot and then remove the back panel to get to the battery and put a tester on that.
     
    1 person likes this.
  5. OP
    OP
    Kay187

    Kay187 Member

    Messages:
    55
    Joined:
    Aug 31, 2012
    Location:
    Scotland
    Car:
    S-class 320 CDI
    I managed to get the battery tested by a local Kwik-Fit who confirmed the starter battery is faulty. It's not holding a charge and on it's last legs. Looking for a replacement now so will report back once changed to confirm it all sorted. Thanks for all your help :)
     

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