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Discussion Starter #1
Hi I recently had to jump start another car from my SL55. I used the starter battery with engine on. Positive was connected to battery on SL and negative to strut.

20 min later I got a red warining on the SL.

What could I be looking at?
 

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If you're lucky, you overloaded and blew the VR. Don't drive it far, it will strand you.

Have the charging system checked. Alternatively you can pull the alternator and have it tested.

Good luck.
 

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If you're lucky, you overloaded and blew the VR. Don't drive it far, it will strand you.

Have the charging system checked. Alternatively you can pull the alternator and have it tested.

Good luck.
Wow, you have just totally discouraged me from ever jump-starting anyone else!

Thanks for this :)
 

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Wow, you have just totally discouraged me from ever jump-starting anyone else!

Thanks for this :)
Well, there is procedure in your owners manual for jump starting,see attached. The procedure says to connect the cables directly to each battery. The only thing you did different was connect Negative to the strut. Maybe VR (voltage regulator) got confused during the process?? Try a reset by completely disconnecting the starter battery from the circuit and follow the side window and ESP resync procedure in your manual.


Good Luck,

Bob
 

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^^^ You'll note that those are the procedures for jump-starting YOUR car.

There are no established procedures for using your car to jump start another. To my knowledge that is not recommended on modern MB vehicles.

Good luck.
 

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I know it is hindsight but next time you may want to consider not having the engine running while jump starting. I have used this method on other modern cars with no problems.
 

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I know it is hindsight but next time you may want to consider not having the engine running while jump starting. I have used this method on other modern cars with no problems.
Not running the engine further drops the voltage, raising the current needed to start the other car, this will increase the damaging factor when it comes to fuses, current limiting components, etc.

R230 has enough elecrical problems on it's own, without lending its electricity to other vehicles... for that, there are jump start boxes, or AAA

OP; You need to check your fuses, particularly the high current 100A and 200A junctions in the passenger foot area.


Next, check the DC-to-DC circuitry, and switching circuitry. A scan with SDS scanner will be handy...

if all else fail, you may have fried the diodes in your alternator, this is not a direct result of jump starting, but because your alternator was failing, and diodes are half fried, the extra current needed by the jump start came as the straw that broke the camel's back...

Red waring is ALWAYS a problem with the FRONT battery charging system, to start with the battery itself, and work your way back to the components and alternator...
 

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Discussion Starter #9
I really appreciate all the replies. Thanks!

I have read and attempted to clear the codes today, but they still remained. Maybe it was a bad indie scanner that couldn`t clear them, but I also disconnected both batteries and that didn`t clear the codes either. My confusion about the codes is because their status is always displayed as "saved", not as "current".

Anyway there are 4 codes, one says starter battery fault others relate to 3 CAN failures with different modules (SAM, etc).

Both batteries show good voltage and they are surely being charged. Engine off 12.8V on 14V. So the alternator is most probably good, which isn`t much of a relief since my next guess is battery control module in the trunk, which is expensive and not in stock.
 

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What was said before all still apply

How did you end up with that light? Front battery removal? Jump starting at rear battery? Over charging at front?
 
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