hrmjay

Hi All,
I got the electrical consumers switched off malfunction today. Both batteries are less than 1 year old and the alternator was also replaced at the same time (last September). Drove the car 2 days ago and everything was fine.

Checked the voltages as follows:
Not running:
Main battery 12. 8v
Aux Battery 12.7v

Running idle:
Main battery 13.5v
Aux Battery 12.7v

Took the car for a quick run - about 5km (about 10 - 15 minutes). When I came back and checked the malfunction message was gone. Checked the voltages again and got the following:
Not running:
Main battery 12. 9v
Aux Battery 12.8v

Running idle:
Main battery 13.9 - 14v
Aux Battery 12.8v

Noticed that the running voltage was higher than before. Am going to check again tomorrow morning when the car has been sitting a day and half to see if it is a parasitic draw.

Any other suggestions to check?

Thanks in advance
Roshan

cetialpha5

Would probably help if you mentioned the year of the car. The pre-face lifted cars had the battery control module that also went bad. The idle voltage doesn't mean much, car is just in idle and can't generate much power anyway due to the lower rpms. It charges while you're driving. If the battery is being charged, you're going to get lower voltages, once it's more charged up, the voltages go up. Also rpms different between hot and cold. Again idle voltages don't mean much, as long as it's charging it's fine. The voltages before starting look fine, normal voltage is about 12.7 fully charged anyway.

nd-photo.nl

Charging should be done with 14.1-14.2v. I would change the voltage regulator first. The batteries are probably fine. I created a video on the W219 platform on how to swap out the voltage regulator.

nd-photo.nl

If the voltage regulator is fine, it could also be:

- Alternator itself
- Battery Control Module (BCM)
- Earth straps/earth points

Could also be parasitic draw, but my first suspect would be the regulator and/or BCM. If you want to monitor the battery, add a battery guard. I can highly recommend this, so you can see what is happening with the battery voltage.

hrmjay

Hi,

Thanks for the suggestions, will definitely get those checked.
As an update, left the car overnight and the message is back.

nd-photo.nl

Then you definitely have some draw. I posted this a couple times, as I was also searching for a drain:

I also had a power drain issue on my CLS55, to be honest I am not sure what I exactly did to solve it, but its highly strange that you cannot access the AGW with your Autel. I also have an Autel and was able to access it and code it where necessary. Some things:

-I also changed my alarm siren/horn. It wasn't working properly anymore and is a known culprit for power drain
-The CD changer needs to be connected with the power cables, else the headunit wont turn on. You can test this easily by drawing the fuse for the CD changer
-If you disconnect MOST components, you also need to adjust the coding for it. Else the AGW will expect the component to be there
-I also removed my phone + cradle in the arm rest. It always felt warm, meaning it was using power.
-I also replaced the BCM with the newest revision (I bought a 2nd hand from a 2007 E-class)
-I also replaced the AUX battery relay under the scuttle. If the AUX battery isnt charged properly, then it will keep asking for power from main battery if I am not mistaken
-I disabled the Interior Motion Sensor for the time being
-I serviced all (or almost all) earth points in the car, removing any corrosion and scuffing them up

[edit]
And:

I was also searching for parasitic drain. Some things:

- Search on Youtube, there are quite some videos on this topic, especially for W211
- Seat control modules are a common culprit, you can test this by pulling out the fuses and checking the draw
- Alarm siren is a common issue, with age the onboard batteries will fail to hold charge. The alarm siren will keep requesting current from the car, preventing it from sleep and draining the battery
- Audio Gateway is a common issue
- Navigation unit can cause drain
- Voltage regulator can cause drain
- BCM can cause drain
- AUX battery can cause drain
- AUX battery relay can cause drain
- non-MB Original alternator can cause issues! There was a thread in W211 AMG section not too long ago if memory serves me right

I replaced my BCM (2005 CLS W219) with a BCM from a 2007 E-class W211. Also replaced the AUX relay, alarm siren, both batteries. I disconnected all Tele Aid/Phone capabilities and fiber looped out the components I dont need (you also need to code them out).

I can also highly recommend a bluetooth battery guard, it gives insight what is happening with the battery > https://mbworld.org/forums/c219/8443...ml#post8860681

hrmjay

Hi All,

Update to the parasitic draw. Turned out it was the Parktronic control unit. With everything powered off there was a draw of 2.8 amps. Fitted a used unit (unfortunately new not available), the draw reduced to 0.061 amps.

Thank you everyone for the assistance.

Roshan