I am getting "Battery Protection: Convenience functions temporarily unavailable" if the e320 CDI sits for a few days. The message goes away after that. The battery is only the second battery the car has had and was installed by Mercedes in 2006 under warranty when the first failed.

I am guessing the battery is starting to die given the age and really do not want to wait for the coldest part of the winter to prove my hunch.

The battery tested OK after I drove 50 miles to a dealer to have the brake fluid flushed. I will be back at dealer next week and have been offered a new Merc. battery for $190.....correct Group 49 AGM and they will install it for free. Should I go ahead and get the new battery or wait for the existing one to fail?

The least expensive like replacement I could find was Autozone at $150 and they will do install too but I am sure they do not know how to reset the various systems.

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-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

Are you talking the large main battery or second small battery under the hood?

Usually when the little battery goes the message is red.

Back one is just comes on as a normal message.

Loose/corroded battery terminals can cause this initial message.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

You thought about it if you wait you'll be kicking yourself when it fails.

It is the large main battery in trunk. Good point about already thinking about it. Better to be proactive. I think the $50 price difference is worth it to get the proper Merc. battery and have it installed by techs. who should know what they are doing.

__________________
-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

Recommend dealer installed battery now.

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Present
1987 300SDL
1991 300SL
1990 560SEL
2001 ML320

Past
1969 200D 1979-82
1983 300SD 1984-85
1972 250C 1982-02
1995 S350 2011
1997 S320 2012

Awfully nice of your battery to warn you that it's on it's way out, and awfully smart of you to listen to it's warning.

Definitely replace it, 8 years on a battery is a darned good run. I replace mine between 3 and 5 years.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap