Unexplained Battery Power Loss!

[EddieHarrald]

How much the drain current is?

One not fused place is breather heater, should be rather easy place to unplug and test.

I recently read memory seats would have two voltage feeds, where another one is not fused, so unplugging seat fuse wouldn't isolate the draw if another circuit is faulty. I have not yest verified if that's true.

Electric heater boosted in air duct draws huge amount of current if short circuited and is easily seen in current reading.

Have you got yor aux battery isolation relay checked? If aux battery is again bad and relay jammed, it will draw main battery.

How much your alternator is charging. W211 have couple of different specific regulator packages, and wrong type is not communicating with car (though it should not cause draining and limp mode charge is 14,3V constantly).

No aftermarket radio, or alarm fitted? No dash camera?

Thankyou! I will pass your Comments on to the Garage on Monday !!
Does anyone know if A Mercedes Diagnostic Computer, Will detect the Fault ??

 

[mersum1es]

No, if pulling fuse testing is true and none helped (except those heater faults are diagnosed). If test has been in haste (car should be go to sleep every time after fuse is put back, this will take 5-10 minutes), fault could be still there. As said berfore acceptable limit is 60mA, when car is 'awake', draw is somewhere 0,2-0,5 amps. Sometimes faulty module can be seen in fault codes too, it is true. If current draw is intermittent, it will be a tricky one to catch.

 

[EddieHarrald]

No, if pulling fuse testing is true and none helped (except those heater faults are diagnosed). If test has been in haste (car should be go to sleep every time after fuse is put back, this will take 5-10 minutes), fault could be still there. As said berfore acceptable limit is 60mA, when car is 'awake', draw is somewhere 0,2-0,5 amps. Sometimes faulty module can be seen in fault codes too, it is true. If current draw is intermittent, it will be a tricky one to catch.

No, if pulling fuse testing is true and none helped (except those heater faults are diagnosed). If test has been in haste (car should be go to sleep every time after fuse is put back, this will take 5-10 minutes), fault could be still there. As said berfore acceptable limit is 60mA, when car is 'awake', draw is somewhere 0,2-0,5 amps. Sometimes faulty module can be seen in fault codes too, it is true. If current draw is intermittent, it will be a tricky one to catch.

Hi, Many Thanks for your Swift Reply, The garage where the car is, is closed until Monday, but I have spoken to the Boss, and he is going to get another Technician to look at it on Monday!
This problem is turning in to a real Nightmare, and taking the Joy Away from owning a Lovely Car !!
Many Thanks for Your Advice, and Input !!
Eddie.

 

[EddieHarrald]

How much the drain current is?

One not fused place is breather heater, should be rather easy place to unplug and test.

I recently read memory seats would have two voltage feeds, where another one is not fused, so unplugging seat fuse wouldn't isolate the draw if another circuit is faulty. I have not yest verified if that's true.

Electric heater boosted in air duct draws huge amount of current if short circuited and is easily seen in current reading.

Have you got yor aux battery isolation relay checked? If aux battery is again bad and relay jammed, it will draw main battery.

How much your alternator is charging. W211 have couple of different specific regulator packages, and wrong type is not communicating with car (though it should not cause draining and limp mode charge is 14,3V constantly).

No aftermarket radio, or alarm fitted? No dash camera?

Hi, I have already posted a Thankyou Message, but it Doesn’t seem to have gone Through !
I will get the Garage, to check your suggestions when they open tomorrow, and Hopefully they will Now Find The Fault !!
Meanwhile Thankyou Again!!
Eddie.