A series of events occurred.
1. I have bunch of free time coming up and was thinking of a project.
2. I was at a seized car auction where a nice spec'd 2006 CLS55 AMG was sitting unloved, dead in the water and a bit rough but straight bodied. Battery was dead but I got it started and drove it the 100 yards I could drive it. Nothing was screaming at me. My pocket OBD said it was clean. It was a California car.
3. I bought the car cheap. 145k miles and most things work.

I now have it at home, runs well but am starting to sort through the issues (driven about 100 miles and a few screen codes have come up). Some easy and small, some more problematic. I work on cars for fun and have wrenched for years but never a MB. It has an oil leak. Gonna chase that down once I get it up in the air. It has a coolant leak. see previous. All the fluids etc are an early swap out.

The current one I am working on is the "red battery light- visit workshop".
1. The batteries are both new and check out for voltage/CCA. The previous owner obviously had a major subwoofer in the trunk and there is an additional 500W 12V battery in parallel for that.
2. The car has been jumped a few times. It sat for 6 months.
3. My OBD alternator test tests out 14.4V.
4. The trunk battery when the car is running is over 14V for charging.
5. But the DASH says 12.2V and when I tested the aux battery upon start up it goes 14V+ then dips within 10 seconds to 12.2V.

Hoping someone has an idea and its a simple fix.

Also looking to buy a OBD2 scanner under $200. Got ti down to Launch x431 Elite Pro and Foxwell NT530. Suggestions are welcome. Trying to keep an uncommon spec car on the road. My 2nd owner 1991 Eagle Talon TSI AWD now has competition for my attention

 

moved to C219 AMG forum...

 

Welcome to the forum and the world of AMG. If you aren't aware the C219 is based on the same year W211 E55 but with different sheet metal. There were a lot more of the w211 built than the C219 so much more traffic and eye ***** on the W211 platform page. Here's the link to that page https://mbworld.org/forums/w211-amg-81/ See you over there.

 

Welcome! Please check my build thread, I have done a lot of (preventative) maintenance and documented almost everything. Hopefully that will also be of use to you

Couple things I can think off
- health of the aux battery is bad and it should be replaced
- the aux battery relay is done and this results in the aux battery not being charged properly

Visit workshop message will be the result of the low voltage warning of either one of the batteries. Get both batteries tested or better yet, replace both of them with fresh AGM batteries.

 

Thank you both of you. Will read the e55 forum. Am now reading your build thread, nice car. Hopefully i can get this back to looking nearly that good. It is a good start point. Black on black color with Alcantara options. Both batteries are lass than one year old. Both charge and load test out above their CCA, (rear 1075 and front 275). The rear is an AGM the front not. I could try replacing it. Am away for next 15 days with work but then off for a month working on this. Parts should all be here by then.

 

Thanks man, happy to help if you run into issues.

Ah good, both batteries have been tested

 

Do you keep a float charger on the car when it is not being driven daily? Even without any additional parasitic draws, these cars use fairly high current flow when 'asleep'. Without a float charger on the car, after few days check the voltage of both batteries before starting the engine. Once the car has been 'waken up' battery dis-charge is fairly high as all of the controllers are then powered and talking to each other through the multiple networks in the car. So, plan in advance to have easy and quick access to both batteries and don't open a door, hood, or trunk until you are ready to test. Add-on elecrtonic components can cause a non-sleep situation which draws down the main battery.

If you aren't aware, the second small battery under the hood is only there to provide a back-up power source for the electronic braking system. It is only called in to help if the main electrical system and battery do not have sufficient power to operate the brakes. Under proper working conditions there is no draw on that battery and due to its small size only takes a brief charge to be fully charged (alternator has an 180 amp rating). Your reported charge of that battery is in the correct range.

 

This document has been shared before on MBworld about the dual battery system