I broke my C220 CDI

stawho

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Jul 14, 2011
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C180
Hi,

The story is: I bought a car that happened to have a battery drain. So I took out the original battery, connected small spare and started diagnosing. Everything was fine so far. Eventually I narrowed the problem down to fuel flap/cigar lighter/interior lights. Took out those three fuses and the drain stopped. Car was left on spare battery for a week or so. I couldn't drive it at the time but was cranking it daily to make sure battery isn't drained.
Finally I decided to charge original battery and fit it back. And this is when disaster came. After replacing the battery car won't start. What's happening is:

- when I disconnect the battery for 5ish minutes, then reconnect, put key into pos 1 I get the radio, working windows (and suppose all the rest is working too)
- after turning into position 2 I can hear the noise from under the engine cover, then a second later 'click' like a relay and everything goes off. dashboard starts going funny with meters having life of their own
-take the key out, put back and into pos 1 and I get 'Restraint System Malfunction SRS'. At this stage it seems like there's lots of load on battery, i.e. windows hardly move, when switching indicator lights dashboard dims etc.

In addition to this, boot won't open. Central lock won't work unless I use emergency key to lock/unlock, then it starts picking up.

Basically looks like total electronic madness, like if it reset. What could have happened and is there any way I can get the car to at least start so I can take it to garage?
 

NOMONEYBUTAMERC

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Simplistic point of view , but would appear that the original battery is not holding charge , especially if car was starting ok on a smaller battery .Have you tested the battery?
 
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stawho

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C180
yes, I tested original battery. charged up full and was holding 12.6V. besides when I put it back it was just disconnected from the charger (not more than 15 mins between disconnecting from mains and putting to car)

[edit]
having said that I'll try topping up the spare battery and jump starting

[edit2]
...after opening boot from the inside...jump leads are inside...grrrrrr
 
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Ted

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No load voltage check will not diagnose a faulty battery check. You need to check the voltage under load to see of it holds up.
 

Stan the Man

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W205 C250d Sport Premium + Auto
Hi,

The story is: I bought a car that happened to have a battery drain. So I took out the original battery, connected small spare and started diagnosing. Everything was fine so far. Eventually I narrowed the problem down to fuel flap/cigar lighter/interior lights. Took out those three fuses and the drain stopped. Car was left on spare battery for a week or so. I couldn't drive it at the time but was cranking it daily to make sure battery isn't drained.
Finally I decided to charge original battery and fit it back. And this is when disaster came. After replacing the battery car won't start. What's happening is:

- when I disconnect the battery for 5ish minutes, then reconnect, put key into pos 1 I get the radio, working windows (and suppose all the rest is working too)
- after turning into position 2 I can hear the noise from under the engine cover, then a second later 'click' like a relay and everything goes off. dashboard starts going funny with meters having life of their own
-take the key out, put back and into pos 1 and I get 'Restraint System Malfunction SRS'. At this stage it seems like there's lots of load on battery, i.e. windows hardly move, when switching indicator lights dashboard dims etc.

In addition to this, boot won't open. Central lock won't work unless I use emergency key to lock/unlock, then it starts picking up.

Basically looks like total electronic madness, like if it reset. What could have happened and is there any way I can get the car to at least start so I can take it to garage?
Yes, use the 'small' spare battery. The original battery is defective, probably a dead cell.
 

rassi

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Jul 17, 2011
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C300 CDI 4matic
Is this on a W203? If so, you have probably blown the rear SAM module, which controls a lot of things such as fuel gauge, wipers, indicators, central locking, etc. Do a Google for this.

Don't ask how I know - brother in law's W203 that I borrowed last week is still being repaired after a flat battery and subsequent jump start that resulted in all of the above, to the tune of lots of €€€€ :(
 
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stawho

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It was the battery after all, I guess Occam's razor still stands :)
All though I found out that apparently you should never jump start from second battery but only using booster pack?
 

Diesel Benz

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All though I found out that apparently you should never jump start from second battery but only using booster pack?

Where did you find that? Why would proper use of a second battery be worse than a booster pack?
 

Chrishazle

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W203's are finiky about voltage spikes when jump starting, there's quite a lot about it on here and t'other side. Result, as above, can easily be blown rear SAM.

There's a second Pos terminal under the bonnet, so for a battery change, connect up a spare decent battery to this and the top of the suspension, remove (and tape, they're still live!) the terminals from the battery to be removed, replace battery, re-connect terminals, disconnect spare battery.

For jump starting, you have to be careful not to get a big current surge when connecting the booster pack or second car. Some booster packs are "soft start" so OK, others are not!

Procedure I've seen for using a second car is :
Do not have engine running on second car
Turn on main beam lights on dead car (sounds daft, but it's to minimize surge through the SAM)
Connect jump leads, wait a while
Start second car, wait a while
Start dead car
Turn off headlights.

I'm no electrical expert, but found the above by searching here and on t'other side when I had battery problems!
 

jaymanek

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W203's and batery drains are a common problem... Can be any one of the numerous modules and the fuse that is causing the drain is just a starting point!

We have had them to be seat modules, door modules, any one of the SAM's....
 
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stawho

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Where did you find that? Why would proper use of a second battery be worse than a booster pack?

It was explained to me like this: If you connect second battery and the car cranks, alternator can see increased battery capacity and will provide more current. Then when second battery is disconnected the current remains at higher level and can blow up electronics.
 

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