Auxiliary Battery Malfunction

[anonymous-user]

Anyone had the "Auxiliary Battery Malfunction" alert come up on the instrument display? Car is a current model C-class (W 205)

It seems to be a known issue and isn't actually a battery at all.... It's a capacitor module that's involved with the start/stop system.

Last year I solved it by replacing the main battery. This time I suspect the Auxiliary module itself even though start/stop still works most of the time.

Anybody changed one?

[JimmyR1]

Had it changed under warranty on an a W212 E63S, no questions asked. It is a common enough issue so if you out of warranty you might be able to get some form of goodwill if your dealer is in a good mood.

[anonymous-user]

Interesting - it does seem a well known problem.

Looks as though the part is reasonably accessible (good old Youtube!) and not too expensive so I think I'll sort it this week if the weather behaves itself.

[anonymous-user]

Swapped the part out today. Easy job in itself although dismantling lots of trim to get to it was PITA, even with the Youtube guidance!

The warning message on the dash has gone immediately.

Bit of a result at £85.20 for an exchange part from Mercedes.