W221 Rear battery

[alexanderfoti]

Hi all

My headunit is playing up (harmon kardon amp), but I have noticed it only does it when the car is not driven for a week or more. If driven frequently its not an issue.

I have also noticed that the rear battery, when I happen to check on it, is at 11.9V (flat!).

The car drives, unlocks and behaves as normal otherwise (Starting from the front battery).

Does this car give "consumers offline" message like the older cars, or do main battery drains go unwarned?

 

[John Laidlaw]

Very good question Alex, interested to hear anyone answer, I don't know....

 

[Botus]

no message on dash...

if you have the comand on for 25 to 45mins or so (without the engine) then it comes up with a message I'm turning off, which you can override

at under12.3v every module throws codes

 

[alexanderfoti]

Ok so do a quick scan and see if I have undervoltage codes on all the ecu's

 

[Botus]

lidl are doing an inverter generator....

only £130 could put that in the put and leaving running permanently... might just be able to keep on top of the std battery drain

 

[alexanderfoti]

hehehe! Neighbours might give me more unusual looks than they already do!

Its such a pain in the arse location to diagnose battery drain on. Have to pull some long cables out past the boot lid so I can lock/unlock the car and watch it sleep.

 

[Richard Moakes]

But of a thread resurrection here, but did you find the drain? What was it?

 

[alexanderfoti]

But of a thread resurrection here, but did you find the drain? What was it?

Rear AMP!