w203 cdi constantly draining battery power

rd123

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May 27, 2011
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5
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mercedes
My w203 220cdi battery is constantly going flat. It doesnt hapen within a few hours but if left for over about 8 hours or so it will start to show signs of strugling to start and any longer than that it doesnt start at all. Been on star at mercedes and it is not any sams. I also found out that interior light was causing a drain so removed fuse for that and that seemed to help a little but it is still draining power from somewhere. Could someone help with any info of what it could be, thanks.
 
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rd123

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May 27, 2011
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mercedes
would having the wrong size of battery be causing a problem. I bought a new battery a couple of months ago from euro car parts and it seems to be workin well. I then had a look in halfords and there battery is a bigger size. I am not to sure what the starting amp is in the battery i have just now.
 
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rd123

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May 27, 2011
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mercedes
No, the only electric parts of the seats are to adjust the back rests and to raise and lower the height of the seat. To move the seats back and forth its manual.
 

effbee584

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Mar 5, 2011
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Norwich
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Jag XF 3.0S and 10 yr old Micra 1.2 auto with Air Con.
There must be something on when you leave the car locked. Try taking out bulbs such the one in the glovebox and boot area, turn the radio off rather than just the ignition off, and any other electrics you have fitted, see if things improve. You probably need an auto electrician to check out power drain on the battery with everything off, and then track down the problem. Good luck. I doubt if the smaller battery is the cause, as long as its spec is as in the handbook.
 

Shellboie

Member
Joined
Oct 19, 2011
Messages
36
Car
w203 C-class estate
My w203 220cdi battery is constantly going flat. It doesnt hapen within a few hours but if left for over about 8 hours or so it will start to show signs of strugling to start and any longer than that it doesnt start at all. Been on star at mercedes and it is not any sams. I also found out that interior light was causing a drain so removed fuse for that and that seemed to help a little but it is still draining power from somewhere. Could someone help with any info of what it could be, thanks.

Once a battery has been run to nought a few times, then they never fully recover. You may need a new battery!! Had this on another car, new battery... problem solved. Make sure you check for drain though as well otherwise this one will go the same way.
 

Diesel Benz

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Feb 3, 2006
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4,207
Location
Europe
Car
222.132 & 213.012 & 906.633
My w203 220cdi battery is constantly going flat. It doesnt hapen within a few hours but if left for over about 8 hours or so it will start to show signs of strugling to start and any longer than that it doesnt start at all. Been on star at mercedes and it is not any sams. I also found out that interior light was causing a drain so removed fuse for that and that seemed to help a little but it is still draining power from somewhere. Could someone help with any info of what it could be, thanks.

How did you measure the interior light causing extra battery drain? Some cars had problems with COMAND in which case the OCP also remained on but I think this was more of a W211 issue.

An incorrect battery size would not cause extra quiescent current, you should figure out more accurately where the current goes when the car is sleeping (before you purchase a new battery, if even needed).

The electric water heater on CDI models is also prone to fail but usually it draws a very high current, making a good battery flat even in a few hours. Memory seats control unit would have been a good candidate as suggested above, "unfortunately" does not seem to be your issue.

These quiescent current problems usually do not trigger any fault codes. Later models log the control unit that keeps a CAN bus alive which often helps finding out the issue.
 

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