Just picked up this c320 and batterey goes dead overnite sometimes anything common to this car that causes it??

 

battery is new and charging system was ok when tested. mechanic cant figure it out......

 

Check the following post:

https://mercedesforum.com/forum/merc...isaster-50251/

I hope you get this resolved.

 

Hi friend the battery on my C220 is huge (100Amp/hour). This means that it can supply 100 amps for one hour or 10 amps for 10 hours (because 10 amps x 10 hours = 100amp/hour). So if your battery is going flat over night (say 12 hours or it could be much less than that) then something is pulling 8 amps (or more) and is potentially getting very hot. Obviously the lights are not on (headlamp bulb will pull 5 amps each) so you are looking for something like the heated rear screen staying on or a heated seat remaining active.
To be honest there are not many things that pull that sort of power on a car which would go unnoticed. The electric fuel pump may pull 6 amps but you would hear that. As I say, heated rear screen could pull 15 amps, heated seats 10 amps each, if you have a diesel the heater glowplugs could pull 10 amps each (i.e. 40 amps in total). I would suggest identifying some of the circuits you dont normally use and having made a note of the position and rating of the fuse....pull it out and see how you go. It is possible you may have a power sunroof whose motor has developed a fault and is always trying to open, the motor does not turn and make a noise but it is sucking power. By pulling the fuses and leaving them out and seeing if the problem goes away would be a good starting point.
If you have an electrician with a reasonable ammeter you could disconnect the positive terminal of the battery and connect this in line (but DO NOT crank the engine else the meter will be damaged). The ammeter should read a small residual current (perhaps 0.5 amps) which is keeping the ECU alive -central locking and alarm system active. If you are seeing amps flowing (e.g. 5 amps) i suggest a friend watches the meter while you systematically pull the fuses one by one until the current drops off to less than 0.5 amps. Whatever that fuse was is the source of the problem. With an ammeter it sould be 10 mins work to find the dodgy circuit, fixing it is a different matter. Hope this helps, Gary (UK).

 

2002 C320 Bat drain. Not in seat modules. I hear a faint hum or small electric motor noise coming from the overhead at the interior lts/sunroof switch area. Any ideas what this is? Where can I disconnect the sun roof module?

 

It's called an OCP (Overhead Control Panel), which is also a common problem on 203 chassis...just like the ESA (Seat Modules). Check with your ammeter before buying the part. Always test before replacing!!

 

Hey guys and girls a couple questions about a car I'm looking at.
Looking at a 2002 c230k coupe that has the electrical problem draining the battery. He has not looked into it yet to see the problem at all. I have to say the car is clean inside and out with 200k miles and the price is scrap price that I can get it at. It is the super charged motor and said it was all sound and great to drive. My mind is telling me to jump on it and it will be a great car for many more miles and my wallet is worried lol. So let me know if you think its work buying and making a decent work car out of it.


Thanks

 

The absolute most important thing here is to get a PPI report from an independent shop. The car could look amazing on the outside and be a nightmare under the hood. This report will also likely tell you how much the draining issue will cost resolve.