W203 Battery draining

[Starky]

Recently, on starting my car the battery has been completely flat. I've managed to get friends over to give the car a jump start, and have taken the car for a spin to charge the battery.

Everything is fine for a few days, then, again the battery is flat. So another call to a friend and a jump start later the car starts, but the prosess happens all over again.

I've disconnected the electric seat module thinking this may be the cause of the battery drain but no joy as it has happened once again.

So my question is, what are then possible culprits? Could it just be a simple fact that a new battery is required?

The car will hopefully be going to a garage as soon as my s/c bearing comes over from the US, so if any body can help before hand that would be great.

 

[WG M-B]

First things first.....
Check the charge rate is ample. It should read around 14volts
Then load test the battery. Surface voltage is not suffient, it needs load testing.
If the above are ok then you need to start looking for a drain

 

[Starky]

First things first.....
Check the charge rate is ample. It should read around 14volts
Then load test the battery. Surface voltage is not suffient, it needs load testing.
If the above are ok then you need to start looking for a drain

Thanks, but I don't think I have the correct test equipment.

 

[pingping]

get a new battery ,you may be looking for ages for a drain fault which may not be the case,could be a knackered battery and thats it,at least you will know for certain if its a drain fault then you can start hunting for it.

 

[matty.13]

The drain will be the electric seat modulator . I had the same thing theres a thread on differnt fourm that explains everything (sorry i dont have the link) it an easy fix though jus cuting and splicing a couple of cables.

 

[WG M-B]

These are not logical or cost effective approaches. Do not buy a new battery before you know it's had it
The seat modules are a common cause of a drain but it is not always the seat module
Ring around locally and get your charge rate tested and battery load tested first
Even an expensive garage should only charge a tenner to do this for you

Then if that's all good start looking for a drain

 

[Starky]

I've disconnected the seat module but joy, thanks any way.

Thanks for the info alf looks like I'll have to give it a go.

 

[fjmrf]

same in mine..

The drain will be the electric seat modulator . I had the same thing theres a thread on differnt fourm that explains everything (sorry i dont have the link) it an easy fix though jus cuting and splicing a couple of cables.

This was exactly what was happen on my one. I made a new electric connection in the seat module to it got energy only when the ignition is on (search here and you will find the diagram) and I got the problem "solved".
But the true is: the only solution is a new one. Yet, it can be the alarm. You could use a amperemeter to measure the drain of battery when in stand by. A normal stand by is around 0.17 A, anything more is a problem. I made it to find the problem in my one. You can by one in Maplin for £10,00. If you don't have knowledge of electricity the exit is: go to a garage.

Best luck on it.

(BTW: I've the pictures of all my process, if you wanna let me know and I find and post it).

 

[Neil Mackay]

I've disconnected the seat module but joy, thanks any way.

Thanks for the info alf looks like I'll have to give it a go.

Have you unplugged both of them?? My passenger one is knackered! I've also had the alarm siren pack up too! C32's seem to have an inbuilt self destruct when they reach a certain age....

 

[Starky]

Have you unplugged both of them?? My passenger one is knackered! I've also had the alarm siren pack up too! C32's seem to have an inbuilt self destruct when they reach a certain age....

Hi neil, yes i have unplugged both of them still no joy

I know what you mean about the inbuilt self destruct. i seems like im just waiting for the next problem to rear its ugly head, but at the moment the smile it puts on my face when it drops a few gear is well worth it... at the moment.

 

[Neil Mackay]

Hi neil, yes i have unplugged both of them still no joy

I know what you mean about the inbuilt self destruct. i seems like im just waiting for the next problem to rear its ugly head, but at the moment the smile it puts on my face when it drops a few gear is well worth it... at the moment.

Sounds like the sequential pulling of fuses with the meter on the battery is the order of the day! Could be the sensor in the courtesy light cluster? Fuse 3 i think...something on on the canbus is keeping comand awake!

 

[Starky]

This was exactly what was happen on my one. I made a new electric connection in the seat module to it got energy only when the ignition is on (search here and you will find the diagram) and I got the problem "solved".
But the true is: the only solution is a new one. Yet, it can be the alarm. You could use a amperemeter to measure the drain of battery when in stand by. A normal stand by is around 0.17 A, anything more is a problem. I made it to find the problem in my one. You can by one in Maplin for £10,00. If you don't have knowledge of electricity the exit is: go to a garage.

Best luck on it.

(BTW: I've the pictures of all my process, if you wanna let me know and I find and post it).

If you could post the process it would be great, not just for me but anyone else who may encounter the problem. Thank you

 

[SAFC]

If you have an ammeter and know who to use it (Voltmeter in ammeter mode will do you just fine) then stick one lead onto one disconnected battery terminal and the other onto the lead you have disconnected. Leave the other battery lead as is. The drain for your alarm system should be minimal. Open the door while you have this set up and see the difference between current flowing when courtesy light on and similar when courtesy light off. If courtesy light drain the same or more as when door is shut then you might have a problem. If not then I’d suggest your battery knackered. Knackered battery symptoms do vary - so this could be your simple problem.
Good luck.
PS If you don't know how to use an ammeter you’ll have to take the car to an auto-electrician who can measure any drain on the battery as descried above.

 

[Starky]

I use a multi Meter for work, would this do?

 

[elite_504]

Sounds like the sequential pulling of fuses with the meter on the battery is the order of the day!

This is really the only definitive way to get an answer to this.

 

[markjay]

I use a multi Meter for work, would this do?

I believe you'll need an suitable Amperage meter connected between the battery and the car. A simple multimeter won't do as most only measure voltage and resistance and at any rate wouldn't be able to handle the car's Amperage.

 

[WG M-B]

If its a multi meter it should have a setting for amps on there

 

[Neil Mackay]

Finally got round to doing one of the common battery drains repairs! the seat module fix! Pretty easy really! Just follow the guide on mbworld....took about ten mins! Wires out the permanent 12vt feed into the ignition 12vt feed! Electric seat again!!!

 

[BlackC55]

Do you have a link?

 

[Neil Mackay]

Do you have a link?

Link as requested

www.benzworld.org/forums/w203-c-class/1403233-diy-how-fix-your-power-seat.html

Hopefully the link will work lol...