S 350 2004 petrol Battery flat after a few days

[Blobcat]

If it’s intermittent the regulator pack on the alternator is a good place to look. One of the diodes might have broken down and when the alternator stops in that position it can drain quite fast - has that on my 911

 

[AMGeed]

A defective SAM along with faulty power seat motors and door control modules are also causes of a battery drain.

Malcolm (TV) helped me find a drain on my previous car by pulling every fuse and noting the drain. He insisted a 65Ma draw is acceptable. Any more, and after checking all fuses the SAM's were the next item to check.

 

[tich]

Thanks for all your replies.
I’m in the London area but happy to travel to some one who’s not a million miles away!
Tich

 

[Blobcat]

@alexanderfoti could well be your man then

 

[Rappey69]

This has been a fairly helpful thread, even though I gate crashed it

 

[mattkh]

......... One of the diodes might have broken down and when the alternator stops in that position it can drain quite fast - has that on my 911

This has been most educational.
What I want to know is as follows:

When testing for a faulty diode using the 'multimeter-diode-mvolts' test with the alternator still in the engine (and the engine not running), do you have to turn the alternator pulley to the next diode position? How does one know the next diode position. I think there are 4 diodes.
Thank you in advance.

 

[Blobcat]

This has been most educational.
What I want to know is as follows:

When testing for a faulty diode using the 'multimeter-diode-mvolts' test with the alternator still in the engine (and the engine not running), do you have to turn the alternator pulley to the next diode position? How does one know the next diode position. I think there are 4 diodes.
Thank you in advance.

To test the diodes individually you need to take the regulator pack off and apart. You could (with battery disconnected) do a resistance check with the meter through the alternator and if one has broken down it will show a low-ish resistance.

 

[Sean O'Driscoll]

There are any number of devices that can stay active instead of shutting down. Comand is one of the favourites for not switching off and draining the battery - any wet footwells or boot?

Sorry for reactivating an old thread, but your question interests me. I’ve just got a W211 E320 which was fine for about a week. Came out to it one morning to a flat battery. Assumed the battery was faulty so put a new one on. 4 days later exactly same. Now, the boot area was “wet” but I couldn’t seem to see where it may have tracked in, all the opening areas were dry. Is it a common thing that battery drain and a wet boot are linked?

My task this weekend is to try trace the current drain, I’ve recharged the battery and it’s back on, I’ve disconnected the negative for now. I’m going to watch the YouTube video posted along this thread, but is the wet boot a warning sign of something?

Thanks, and sorry again for hijacking an old thread.

 

[Blobcat]

Water and electricity are never a great mix...
Look for leaks around the boot handle trim and/or rear lights

 

[LostKiwi]

Also check around the fuel filler neck. My 129 had a perished rubber seal around the neck that leaked like a sieve and killed the central locking pump below it.

 

[Sean O'Driscoll]

Thanks both, is the theory that the water droplets sitting on the battery short it? Or is the idea that it’s affecting other components in the boot?

I could smear both battery terminals with Vaseline to eliminate that.

 

[LostKiwi]

Other components in the boot short internally, eventually destroying the component but in the short term draining batteries.
My own SL has a drain caused by Comand not turning off completely. For the moment I live with it and leave Comand off (it shuts down fully once the battery is flat and doesn't drain unless switched on again).

 

[Sean O'Driscoll]

Thanks. Maybe my first job is to look for the leak then rather than look for a current drain. I don’t think I have command, it’s the radio with the black dot matrix screen, could this still not be shutting down though? It would be a piece of cake to just pull that fuse and see what state the battery is in in 2 days.

I do think I heard the changer randomly whirring away the other day whilst I was sat in the car, I actually thought to myself should I fill it with discs so it has no work to do?

Cheers.

 

[Blobcat]

Thanks both, is the theory that the water droplets sitting on the battery short it? Or is the idea that it’s affecting other components in the boot?

I could smear both battery terminals with Vaseline to eliminate that.

Water droplets in the battery aren't an issue, it’s water in some connector so SAM module that will be the issue.

My Land Rover batteries work well completely submerged...

 

[LostKiwi]

Thanks. Maybe my first job is to look for the leak then rather than look for a current drain. I don’t think I have command, it’s the radio with the black dot matrix screen, could this still not be shutting down though? It would be a piece of cake to just pull that fuse and see what state the battery is in in 2 days.

I do think I heard the changer randomly whirring away the other day whilst I was sat in the car, I actually thought to myself should I fill it with discs so it has no work to do?

Cheers.

Exactly the symptom I have with my Comand system - the CD changer randomly whirs away.

 

[tich]

Just to update!
I sorted my problem sort of!
Installing a battery cut off on top of battery terminal £5 jobs a good un...lol
As this is my Sunday car,only drive it once every 2-3 month and this certainly works for me.
I know not ideal if someone uses it every day but after being quoted about 700-1500 including parts,I’m sure the cars not worth much more than that.

 

[tich]

Just an update..
I’ve noticed that the command system doesn’t shut off at all even when the keys removed from car!
All other electrical working parts are shutting off after 15-30 mins..but the command system turns on even after an hour ..I tried this without opening the door by leaving the passenger glass down,so as opening a door could activate it.
Tried removing the sat nav disc and leaving it for 30 mins..still command works..
Could this be the source of battery drain and what’s the remedy..as I said before I only use this car once every 2-3 months
Help.!!

 

[peter129]

Hello, iv'e had this problem battery going flat after a few days, fit new battery and same thing happened. thought it was a duff battery tried disconnecting wires from battery still no good until I was told about heater in the engine block.Mine is a 2004 clk 270cdi and the heater is located on the nearside just above the starter, it's a Square block if I remember. For some reason it is wired directly off the battery and the thermostat must have gone faulty and it was draining the battery.A visit to my local garage and a pair of wire cutters cut the power lead taped it up and bingo no more flat battery. I don't know whether its an accessory or a standard fit but it caused a lot of aggravation, worth checking to see if yours has one fitted

 

[tich]

That’s another item to check..
Appreciate your input
Thanks

 

[tich]

Just wondering..
Any member who’s got similar age model s class 2004 model 220 could check and confirm if..
With car locked keys are removed ..leaving the passenger window open..and leaving it for about 30 mins so to make sure everything is gone off.
Then through the open passenger window press the command button on to see if it turns on?
I know the door opening could trigger the system to come on that’s why I said about leaving the open window!
My guess is it shouldn’t come on ..but mine does come on..leading me to believe that’s my parasitic drain.
Btw the seats and windows don’t work except the command system!
Thanks