Sudden cut out

[robmc52]

Don't know if this is the right subforum for this post, had a sudden and total cut out whilst driving yesterday in my W220 32088 CDI. Car was driving perfectly when I heard the interior fan stop, then a pre safe message followed by the red battery warning, then everything went dead. Luckily I was on a very rural French road with no traffic around, so just came to a halt, removed the key, stuck it back in and it fired up straight away and we continued on our journey as if nothing had happened.
I thought at first it may be the battery on the way out, although it's only a couple of years old, will plug the isoft in and check the starting voltage this morning, but would appreciate any input on where else I should check!

 

[Blobcat]

Main battery leads - positive and body earth - check they’ve a good connection

 

[robmc52]

Have checked the battery when starting, it drops to 7.5 volts when the starter turns, then up to 13.8 ish when idling.

 

[mioba]

test the battery 30 mins after a good run in the evening , then test again the next morning before starting.

 

[AMGeed]

As above, the battery needs reading before starting. Anything under 12.0v is low charge.

 

[robmc52]

Thanks for the replies, especially the colour coded chart. Checked the voltage this morning, 11.7 to 12.06, so on the cusp of being knackered I guess. Now comes the adventure of trying to find a replacement in the middle of the Charente...

 

[mattkh]

...... so on the cusp of being knackered I guess. .

Well done for testing how low the voltage goes when cranking.
That is the best test to determine the juice in a battery.

 

[robmc52]

It's quite annoying really, I think the battery was new around 2 and a half, 3 years ago, from the dealers, so it hasn't lasted very well. I'll try a Varta if I can find one locally, they seem to be well regarded in Merc circles.

 

[rich.g.williams]

So the car behaved as if all electrical power was lost? I would be wondering if an alternator fault would manifest like this? Alternator brushes wear down and from then on likely make intermittent contact, Otherwise some kind of wiring/electronics fault. Needs an opinion from an experienced MB electrics specialist

 

[robmc52]

So the car behaved as if all electrical power was lost? I would be wondering if an alternator fault would manifest like this? Alternator brushes wear down and from then on likely make intermittent contact, Otherwise some kind of wiring/electronics fault. Needs an opinion from an experienced MB electrics specialist

I doubt if it's the alternator in this case as it had a new brush pack a few months ago. Taking the battery to get it checked this morning so that will hopefully give a good indication of where the fault lies.

 

[rich.g.williams]

I doubt if it's the alternator in this case as it had a new brush pack a few months ago. Taking the battery to get it checked this morning so that will hopefully give a good indication of where the fault lies.

Consider looking for something that has the ability to as you say "then a pre safe message followed by the red battery warning, then everything went dead" It needs some sort of relay related to the ignition system controlled by a computer bright enough to sequence through the pre warning to total cut out.

Seems you have eliminated the battery and the alternator (very strange battery fault apart from bad contact to battery terminals or battery negative strap to chassis).

Could it be a known safety response triggered by something intermittent as yet unknown.

 

[mattkh]

........ the alternator in this case as it had a new brush pack a few months ago.

That means it is a high mileage car, hence been more exposed to atmosphere, hence a greater chance of rusted earth contacts.

 

[robmc52]

That means it is a high mileage car, hence been more exposed to atmosphere, hence a greater chance of rusted earth contacts.

Hi Matt, indeed it is a high mileage car, 287,000 so far!
I have checked the earth points, in the boot, the wiring under the passenger side carpet, and also checked the starter and cdi relays, cleaning and smearing some dielectric grease on everything as I went. Everything looked good anyway.
I then removed the battery and took it to a nearby E L'clerc Auto centre a few miles away from where we were staying to get it tested. This showed a voltage of 11.9, so I decided to buy a new battery as this looked a bit on the low side as per the chart that AMGeed kindly posted. The new battery is slightly more powerful than my existing one, 105 amp hour.
Incidentally, when the chap in the shop checked the voltage, he asked if I had a stop/start system on the car (it hasn't, being 18 years old!) he thought it was a stop/start battery, which he said was not really compatible, I wonder whether there is any truth in this?
Anyway, since the new battery has been fitted, I've put another 800 miles on the car and it's been running perfectly, in fact I have noticed that when the car is started the navigation starts working immediately, before it used to take 30 seconds or so to boot up, coincidence? Probably!

 

[Botus]

stop start tech is what they tend to call durable batteries capable of high abuse - which suit mercs electrics.... AKA AGM (absorbed glass matting)

if the old one was AGM and you still have it get the lids off and top it up - it will come back to life - they now know how little moisture to add at build to get them to fail to time correctly.... the originals did 9 years, far too long... so put a third of the moisture in - et voila

 

[robmc52]

stop start tech is what they tend to call durable batteries capable of high abuse - which suit mercs electrics.... AKA AGM (absorbed glass matting)

if the old one was AGM and you still have it get the lids off and top it up - it will come back to life - they now know how little moisture to add at build to get them to fail to time correctly.... the originals did 9 years, far too long... so put a third of the moisture in - et voila

Thanks for the info Botus. All of the cells are low on fluid, and the innards are the same as the first photo. As I'm no expert I have no idea if it looks ok or not. I like the 'special' caps fitted to it, deliberately made to make it as difficult as possible to remove!

 

[Botus]

these are not wet batteries... they should have damp tissue paper that swells up hiding the black plates - often you come back a day later and it needs another top up - you should NOT have a puddle on top

the lids are a nightmare to get off... it won't spring back to life instanly - it will get happier over a while - a long charge helps...