battery keeps going flat

[striker600]

Another point worth mentioning is that to test that all systems shut down as they should then need to be woken up first. If the battery is disconnected, the reconnected this will not be the case. The method I use is to clamp the battery terminal with a long nose vise grips or similar and connect the metre. Start the car, switch it off, then remove the grips. This then allows the meter to maintain the circuit. If the circuit is not maintained the test may not be valid.
Better again, use a clamp on meter.
Also be aware, I saw a cheap metre that went open circuit for an instant as the range was changed.

Autofix,The first meter i used was a cheep wickes own brand(oh dear)which was fused up to 250ma,thats why the fuse kept blowing as my car had a drain of 1020ma,also i connected it in parallel first time,2nd time in series,which still blew fuse.
I now have a UNI-T multi meter model no. UT33c,which has a 10a max capacity.I clamped the probes with crocodile clamps to the batt -terminal &neg clamp.
As you can see from post #20,the biggest drain culprit is the passenger memory seat.As to limit drain i have disconnected the passenger memory seat fuse,which brings the drain down from 1020ma to 290ma.
Is it possible to have this passenger memory seat unit tested as to confirm its broke,before i obtain a replacement?If anyone could recommend a company besides MB.

 

[Dieselman]

I don't see why any of those circuits should be active with the ignition switched off, I'm sure you have a SAM fault.
iirc the allowable drain is 30ma max.

 

[striker600]

I don't see why any of those circuits should be active with the ignition switched off, I'm sure you have a SAM fault.
iirc the allowable drain is 30ma max.

Thats what i cant understand.the memory seats will work with the drivers door open(ignition key removed).But I made sure the ignition key was removed,all doors closed & interior lights were off during drain test.
Would this fault be with the rear sam? What dose sam stand for? i am guessing as systems actuator modual?Can anyone recommend a company that can test the sam or will it have to be MB?

 

[gbjeppm]

BBA-Reman might be able to help you with the SAM

http://www.bba-reman.com/uk/index.aspx

I have never used them though, so can't recommend them or recommend against.

 

[stats007]

I know a number of people who have used them for cluster and R129 roof ECU repairs - no complaints.

 

[striker600]

Thats what i cant understand.the memory seats will work with the drivers door open(ignition key removed).But I made sure the ignition key was removed,all doors closed & interior lights were off during drain test.
Would this fault be with the rear sam? What dose sam stand for? i am guessing as systems actuator modual?Can anyone recommend a company that can test the sam or will it have to be MB?

Just had a look at this link http://www.bba-reman.com/content.aspx?content=Mercedes_Benz_SAM_Units .Thing is i dont have any of the faults listed.I also looked at this one http://www.bba-reman.com/content.aspx?content=2002_Mercedes_Rear_SAM_Unit_Small_3
But again every consumer connected to the rear sam works.I recon a phone call to bba-reman maybe a good idea.

 

[Stan the Man]

I have just done some drain tests with the muiti meter, connected in series between batt.neg terminal &earth strap.Meter was set to 10 amp DC range.All elec consumers off. 1000 milli amps (ma)=1 amp.(a)

Here are the readings-
Total current drain=1.02amps=1020 milli amps
I then disconnected the following consumers (in turn one at a time)by removing the fuses(using the mb fuse card)and took meter reading

Rain sensor-fuse 9 (is this known as OCP? mb fuse card dose not list OCP,only rain sensor) 0.93a=930milli amps.1020ma-930ma=90ma drain.

Seat adjuster(drivers)fuses 2,21,27. 0.89a(890ma)
1020ma-890ma=130ma drain.

seat adjuster(passenger)fuses 1,22,38. 0.29(290ma)
1020ma-290ma=730ma drain.

I then dissconnected both driver&passenger seat fuses,meter reading was 0.13a or 130ma.

I then disconnected all 3 together,ie.seats&rain sensor fuses.Reading was 0.05a or 50ma. 1020ma-50ma=970ma drain.

My Questions are¬
1.With all the above 3 consumers disconnected at the same time, the current drain is down from 1020ma to 50ma. Is 50ma within the acceptable tollorence?

2.Do i need to disconnect the fuse(s) of other consumers to test for current drain?If so witch ones?

3.Do i need to replace seat adjuster(drivers&passenger)and the rain sensor?

4.How much are the above 3 componants?

Any additional help and imformation would be appreciated.

The quoted figure of 30 to 40mA quiescent current is, I beleive, applicable to your vehicle when fully shut down ie. Doors closed and locked, alarm activated. It takes a finite time for systems to 'go to sleep' and you will not be measuring the correct quiescent current drain until this state is achieved.

It is possible for a faulty unit to keep a sam module awake and waiting for network traffic. This can result in excessive quiescent current drain, due to irregular can activity.

I suggest you connect your ammeter using long leads and clamps to enable you to close the bonnet, leaving the ammeter outside the engine bay. Then close and lock doors and go for a cuppa. Return in an hour to check current reading (by which time all systems should be sleeping)

Then you can begin to selectively disconnect suspect units until the culprit is identified.

Memory seat modules are common culprits as are rear sam modules (yours seems to be ok)

 

[striker600]

Stan the Man,Weather permitting i will carry out what you suggest in post #27 an post a update in due course

 

[striker600]

The quoted figure of 30 to 40mA quiescent current is, I beleive, applicable to your vehicle when fully shut down ie. Doors closed and locked, alarm activated. It takes a finite time for systems to 'go to sleep' and you will not be measuring the correct quiescent current drain until this state is achieved.

It is possible for a faulty unit to keep a sam module awake and waiting for network traffic. This can result in excessive quiescent current drain, due to irregular can activity.

I suggest you connect your ammeter using long leads and clamps to enable you to close the bonnet, leaving the ammeter outside the engine bay. Then close and lock doors and go for a cuppa. Return in an hour to check current reading (by which time all systems should be sleeping)

Then you can begin to selectively disconnect suspect units until the culprit is identified.

Memory seat modules are common culprits as are rear sam modules (yours seems to be ok)

just done drain test(multi meeter connected on 10 amp scale) with doors,bonnet shut & locked,alarm on.
Amps reading was the same(1.02a=1020ma)for the first 1 to 2 minute,then after that reading fluctuated between1.00a=1000ma to 0.99a=990ma.I assume this is When the systems go to sleep.I left car for 1 hour &the reading was the same.I then continued to do the following:-

With doors unlocked but closed & alarm off reading dropped between 0.99a=980 to 0.99=990ma.
I then disconnected the passenger seat memory fuses,reading dropped to 0.13 to 0.14 (130ma to 140ma) i reconnected passenger seat fuses.
I then disconnected drivers memory seat fuses,reading dropped to 0.93a(930ma).
I then disconnected both drivers&passenger memory seat fuses reading dropped to 0.14 to 0.13a (140 to 130ma)
I then disconnected the rain sensor,reading dropped to 0.12 to 0.13a (120 to 130ma)
I then disconnected the central locking fuses,the reading dropped further to 0.04 to 0.05a (40 to 50ma)
I then disconnected the radio fuse (fuse no.64) the reading dropped to 0.01 to 0.02a (10ma to 20ma)

As i said in previous posts,the passenger memory seat is the biggest drain culprit causing a drain of 850ma (990ma-140ma=850ma)
Where as the drivers memory seat is only causing a drain of 60ma (990ma-930=60ma)

My Question is:-
1.Are all the other consumers i tested for current drain ie. rain sensor,central locking,alarm & radio within acceptable tolerance?

its looking like i need a new passenger seat memory controller or whatever its called!
I would like to have this tested to confirm its broke before i obtain a new one.Can anyone recommend anyone other than mb dealers that can test these seat memory controllers? Any comments or suggestions will be welcome.

 

[whestworld]

I had a similar fault. The current draw on my C32 was 3amps and that killed the battery overnight. I discovered it was my air con controller at fault. I removed fuse no. 41 (C32 AMG) and all was fine. I now need a new controller.

 

[striker600]

AS a temporary measure i have disconnected fuse 38 (passenger memory seat adjuster) which brings the current drain down from 990-1000ma to 130-140ma.Im using the car daily&the battery has not gone flat since i fully charged it on 01/02/09.
The air conditioner (fuse 41) dose not seem to be causing any drain on my car.In the near future im going to have the passenger seat adjuster tested/and or replaced.
Can anyone tell me if star diagnostics will show faults with the seat adjusters,ocp(rain sensor) and rear SAM?

 

[blueskywcc]

Hi striker600, this post is a year old. I hope you or someone else read this.

I may have measured current drain incorrectly for my car 2002 C240. I am using Equus 3320 multimeter. Here is what I did.

1. Disconnected the negative cable from the battery.
2. Selected DCmA function on my multimeter. This function has 315mA/250V fuse and measure from 0 to 200 mA according to the multimeter's manual book.
3. Connected the multimeter to the negative cable and to the negative terminal in series.
4. Reading says 0.011 I wasn't sure if this is correct so I did next step.
5. Selected DC10A function on the multimeter. This function is unfused measure 0 to 10 A.
6. Connected the meter in series again.
7. I get small sparks and the reading is 2.0 A.

Q1. Is the second reading correct?

I red some article on the Internet saying that "When the battery cable was disconnected the vehicles electronics lost power, these devices will draw a higher current when they are reconnected (probably, when I connected the multimeter in series). The current will drop as the numerous electronic devices awaken. On some late model vehicles this may take 20 minutes or longer."

Q2. What is the correct way of measuring parasitic current drain on MB vehicle?
Q3. If you leave a multimeter connected for 20 minutes or so, wouldn't it damage the meter?
Q4. How did you connect the multimeter to the battery when doing the drain test?
Q5. If you lock the door and disconnect the negative cable from the battery, does your car alarm sound go off?

Q6. What were the fuse numbers for seat memory and rain sensor?
Q7. Did you pull out connectors under the seat? or just fuse?

Thank you.

 

[Ted]

Q1. Is the second reading correct?
Yes (probably)
Q2. What is the correct way of measuring parasitic current drain on MB vehicle?
This is the correct way. As already said, you may find an additional current flow when first connecting. A constant current of 2 amps indicates either something (boot lamp, interior light?) is turned on, or a fault.
Q3. If you leave a multimeter connected for 20 minutes or so, wouldn't it damage the meter?
Not if the current is within the meter range - i.e. 2 amps on 10 amp range is fine.
Q4. How did you connect the multimeter to the battery when doing the drain test?
I believe that the way you did it is the correct way. It is exactly how I would do it.

Pass, on all the other questions

 

[BlackC55]

The car needs to be locked too and it also needs to go to sleep. That can take up to 40mins