W211 MY2007 E320 CDI - dead dash clocks and no aux battery ?!

[mbdaniel]

Hi all

I've just got in my car after 2 weeks of self isolation due to covid and the instrument cluster is dead !
No warning lights, no display, rev counter / speedo not working etc
Radio, indicators, lights (headlights come on even though the switch is off!), brake lights all work.
Steering wheel functions don't do anything (volume, menus) although the horn works.

Ambient lighting and interior lights appear to be working, dimmer control on the dash doesn't appear to do anything. Convenience functions (get you home lighting, folding mirrors) don't work, although the mirrors do fold using the button on the driver's door.

Car starts and runs fine (although I've got no idea how much fuel I've got, or engine temp. LOL)

I've done some searching and people have suggested that the auxiliary battery might be FUBAR. so I removed the cabin filter and found this : link to image
I thought all W211 models had a second battery that powers auxiliary functions (such as the dash).

I've checked fuses 43/44 and they appear fine.

It's obviously not the 2nd battery, so can anyone suggest what might be the cause ?
It's a bit of a coincidence that the car has been standing for 2 weeks (and they were working before that) if it's not related.

Any ideas ?

Cheers,
Daniel.

 

[Trickythemerc]

I would begin with a battery disconnect and then fully charge before reconnecting. Then if you still have problems a star session is your best bet.

 

[W1ghty]

I doubt any facelift W211 has a second battery ,mine doesn’t .

 

[AMGeed]

The auxiliary battery was backup for 211 pre facelift cars with SBC braking. Not fitted to a 2007 car.

I'd suggest putting the main battery on charge or consider replacing it if its over 4yrs old.

 

[mbdaniel]

The auxiliary battery was backup for 211 pre facelift cars with SBC braking. Not fitted to a 2007 car.

I'd suggest putting the main battery on charge or consider replacing it if its over 4yrs old.

Thanks - it's less than a year old and the green light on the battery is glowing but I have stuck it on charge anyway...

I doubt any facelift W211 has a second battery ,mine doesn’t .

Cheers - didn't know that... would explain why my old W211 had one, though.

I would begin with a battery disconnect and then fully charge before reconnecting. Then if you still have problems a star session is your best bet.

Thank you


Thanks all - fingers crossed !

 

[mbdaniel]

Battery is all charged and the instruments are back to life

I've just done (an essential) 60 miles up and down the A1(M) to blow the cobwebs away and all seems to be good.

Thanks all,
Daniel.

 

[E55BOF]

As you've discovered, the W211 is VERY sensitive to a battery even slightly low on charge, and it can throw up all sorts of weird and wonderful, and apparently unrelated, electrical faults.

 

[esscee]

As said, 211 sensitive to battery voltage dropping off. If you plan on keeping vehicle then it makes sense to get a CTEK battery charger and keep it connected during these "strange times".

 

[W1ghty]

Or a Maypole 7423 charger and save yourself a good few quid