W204 battery drain whilst engine is running??
03-28-2018, 09:28 AM
#1
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W204 battery drain whilst engine is running??
Hello all hope someone can help.
About 2 months ago I went to start my Mercedes c class 2011 plate and on my dash it come up two errors.
Run Flats inoperable and ESP inoperable.
So I turned the car back off waited a minute and it was fine. A few weeks later the car did this again so I turned it off then I was unable to start at all so called the AA. They plugged in to ECU cleared a few minor errors and still struggled to get it to start.
All of a sudden it just come to life and it was fine for another couple weeks then it happened again but instead of turning it off to reset these errors I carried on driving as had to get to work. Mid journey the command unit closed down and I had a low battery error on the dash.
I got the car to work and the battery was flat. I took the battery out and put it on charge for a day in the workshop as I I am also a mechanic/electrician but for the trains, connected it to car and it just would not start.
Called AA out and fuse 7 the fuse that sends the voltage to the contact on starter had blown. So we disconnected the wire going to the contact from the back of front fuse box, and removed the relay that switched the voltage to the contact. Put a fuse in and it did not pop but the second the relay went in the fuse popped.
Tested the relay that was all good, even unplugged the ECU as the coil of relay goes there, ground switch I guess, but the fuse still blew.
I suspect the front SAM is faulty but can all these errors and the battery drain all be linked to the SAM unit or have I got separate problems here?
Any help would be great
Thanks
About 2 months ago I went to start my Mercedes c class 2011 plate and on my dash it come up two errors.
Run Flats inoperable and ESP inoperable.
So I turned the car back off waited a minute and it was fine. A few weeks later the car did this again so I turned it off then I was unable to start at all so called the AA. They plugged in to ECU cleared a few minor errors and still struggled to get it to start.
All of a sudden it just come to life and it was fine for another couple weeks then it happened again but instead of turning it off to reset these errors I carried on driving as had to get to work. Mid journey the command unit closed down and I had a low battery error on the dash.
I got the car to work and the battery was flat. I took the battery out and put it on charge for a day in the workshop as I I am also a mechanic/electrician but for the trains, connected it to car and it just would not start.
Called AA out and fuse 7 the fuse that sends the voltage to the contact on starter had blown. So we disconnected the wire going to the contact from the back of front fuse box, and removed the relay that switched the voltage to the contact. Put a fuse in and it did not pop but the second the relay went in the fuse popped.
Tested the relay that was all good, even unplugged the ECU as the coil of relay goes there, ground switch I guess, but the fuse still blew.
I suspect the front SAM is faulty but can all these errors and the battery drain all be linked to the SAM unit or have I got separate problems here?
Any help would be great
Thanks
03-28-2018, 11:11 AM
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Thanks for your replys, is it worth sending the SAM unit off for repair or better to get a new one. Also would the Run Flat inoperable and the ESP inoperable errors also be caused by the front SAM?
04-26-2018, 10:41 PM
#6
Hello all hope someone can help.
About 2 months ago I went to start my Mercedes c class 2011 plate and on my dash it come up two errors.
Run Flats inoperable and ESP inoperable.
So I turned the car back off waited a minute and it was fine. A few weeks later the car did this again so I turned it off then I was unable to start at all so called the AA. They plugged in to ECU cleared a few minor errors and still struggled to get it to start.
All of a sudden it just come to life and it was fine for another couple weeks then it happened again but instead of turning it off to reset these errors I carried on driving as had to get to work. Mid journey the command unit closed down and I had a low battery error on the dash.
I got the car to work and the battery was flat. I took the battery out and put it on charge for a day in the workshop as I I am also a mechanic/electrician but for the trains, connected it to car and it just would not start.
Called AA out and fuse 7 the fuse that sends the voltage to the contact on starter had blown. So we disconnected the wire going to the contact from the back of front fuse box, and removed the relay that switched the voltage to the contact. Put a fuse in and it did not pop but the second the relay went in the fuse popped.
Tested the relay that was all good, even unplugged the ECU as the coil of relay goes there, ground switch I guess, but the fuse still blew.
I suspect the front SAM is faulty but can all these errors and the battery drain all be linked to the SAM unit or have I got separate problems here?
Any help would be great
Thanks
About 2 months ago I went to start my Mercedes c class 2011 plate and on my dash it come up two errors.
Run Flats inoperable and ESP inoperable.
So I turned the car back off waited a minute and it was fine. A few weeks later the car did this again so I turned it off then I was unable to start at all so called the AA. They plugged in to ECU cleared a few minor errors and still struggled to get it to start.
All of a sudden it just come to life and it was fine for another couple weeks then it happened again but instead of turning it off to reset these errors I carried on driving as had to get to work. Mid journey the command unit closed down and I had a low battery error on the dash.
I got the car to work and the battery was flat. I took the battery out and put it on charge for a day in the workshop as I I am also a mechanic/electrician but for the trains, connected it to car and it just would not start.
Called AA out and fuse 7 the fuse that sends the voltage to the contact on starter had blown. So we disconnected the wire going to the contact from the back of front fuse box, and removed the relay that switched the voltage to the contact. Put a fuse in and it did not pop but the second the relay went in the fuse popped.
Tested the relay that was all good, even unplugged the ECU as the coil of relay goes there, ground switch I guess, but the fuse still blew.
I suspect the front SAM is faulty but can all these errors and the battery drain all be linked to the SAM unit or have I got separate problems here?
Any help would be great
Thanks
If you take your battery into a auto parts store where you live and have them test your battery and they say that the battery is good, then it would sound like to me that your alternator may have a problem or even a combination of the alternator and the Front SAM. Which if it's only the SAM, then you might be able to get the SAM flashed to see if this fixes the alternator to start charging your battery again.
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05-25-2018, 12:46 PM
#8
They can, but you'll have to find someone online, like eBay, to do it for you.
I've seen ebay posts advertising this service. OR you can go and buy your own Star Diagnostic system for $1,500 and do it yourself! LOL
I've seen ebay posts advertising this service. OR you can go and buy your own Star Diagnostic system for $1,500 and do it yourself! LOL
05-25-2018, 12:50 PM
#9
If you take your battery into a auto parts store where you live and have them test your battery and they say that the battery is good, then it would sound like to me that your alternator may have a problem or even a combination of the alternator and the Front SAM. Which if it's only the SAM, then you might be able to get the SAM flashed to see if this fixes the alternator to start charging your battery again.
Most of the time the symptom of a battery draining while the car is running is because the Alternator is not charging the battery due to bad solenoids on the Alternator. Which means you'll have to get. new alternator. But just as how you can have a battery tested at a auto store, they can also test your alternator as well. To see if it is working. Before buying a used SAM and trying to find someone to flash it for you. Have your battery and Alternator tested first.
B.
05-27-2018, 09:28 AM
#10
Super Member
Once you ensure that battery voltage is back to normal range, clear codes and run the vehicle to see if those codes return. More likely they won't (assuming it isnin fact a battery voltage issue).
06-09-2018, 08:24 AM
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Has anyone on here got the electrical schematics for the abs and esp circuits please? W204 saloon c200
No longer believe it is the sam unit that’s blowing the fuse. Bridged the relay and fuse does not pop so suspect faulty relay! However seems like the starter motor has also failed now. When 12V is put on the signal to starter wire the contact moves but no crank! No drain on battery neither when trying to start it.
still showing abs and esp errors! Booked in for a garage Monday!
Will update the thread on the outcome.
No longer believe it is the sam unit that’s blowing the fuse. Bridged the relay and fuse does not pop so suspect faulty relay! However seems like the starter motor has also failed now. When 12V is put on the signal to starter wire the contact moves but no crank! No drain on battery neither when trying to start it.
still showing abs and esp errors! Booked in for a garage Monday!
Will update the thread on the outcome.
06-27-2018, 05:13 AM
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So I got the car out of the garage 2 weeks ago and they took starter motor off and tested it, all fine.
then told me it was the front sam which they replaced and car worked fine for 2 weeks and now bam! Problems come back car won’t start and the same fuse keeps blowing. Phone garage they said it must be the starter motor. Even tho I unplug the wire to starter solenoid from back of sam unit the fuse still pops. I removed the 5 pin relay bridged the 12v to the starter side of switch and fuse does not blow. If I put the 12v to other side of the switch ( the switch has two outputs ) it pops the fuse! The problem is on the drawings it only shows the relay as a 4 pin relay!
Does anyone know what this extra extra pin is actually doing?
06-27-2018, 04:09 PM
#14
Super Member
Have you had the alternator taken off and examined for short maybe coming from there intermittantly, not sure if this alternator has a unit with the brushes you can remove without removing the alternator. Seeing the starter is out of the question, I would clear the alternator also before going further, just in case it causes problems in other stuff(Sam) you want to replace, the alternator is after all a physically working part, and one or other time you going to be confronted by it in any case.
Last edited by Moto_Guzzi; 06-27-2018 at 04:11 PM.
06-29-2018, 11:09 AM
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Thank you for the response I have not had the alternator checked but I think I’m going to have to put it back in the garage! So I will get it checked then. I replaced the fuse today and it started up fine and the car is working.
however I noticed a small amount of smoke coming from the battery junction block after starting and stopping the car a few times! It is the block where you attach the jump leads on the terminal closest to the front of the car.
i have attached a picture but does anyone know where this wire goes too, is it the starter motor? Why would it be getting so hot and drawing so much current?
06-29-2018, 12:12 PM
#16
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Thank you for the response I have not had the alternator checked but I think I’m going to have to put it back in the garage! So I will get it checked then. I replaced the fuse today and it started up fine and the car is working.
however I noticed a small amount of smoke coming from the battery junction block after starting and stopping the car a few times! It is the block where you attach the jump leads on the terminal closest to the front of the car.
i have attached a picture but does anyone know where this wire goes too, is it the starter motor? Why would it be getting so hot and drawing so much current?
