C320 Battery Replacement Problems
 

I originally had problems w my 2001 C320 after my battery went dead. I've resolved most of those problems this past weekend. This may be different for each MDY, but it appears that when your battery dies or you replace it with a new battery, the MB CPU will go into a default mode where nothing works properly:
- the car trunk cannot be opened
- the car's remote only unlocks if pointed directly at the driver's side sensor
- signal lights and emergency lights do not work
- windshield wipers and fluid do not work
- instrument pannel display is incorrect
- error messages for SRS, ESP

However, you can reset the MB CPU by disconnecting the battery cables for a longer period of time (I did it for 24 hours) to drain the CPU of all electrical power completely. Dead batteries cannot start cars but they have enough juice to sustain CPU's. Also when a battery is removed for a short period (ie: to change the battery), the CPU has enough power to retain the error settings.

I reconnected the battery to the C320 after 24 hours and the MB CPU did reset itself. The only error messages were the ESP (which is easy to resolve) and the SRS. Unfortunately, there is no way to resolve the SRS error. It can only be done by a tech w the MB Star sensor. But at least you can tell the MB tech to fix one prob only (and save on the hourly charges) rather than have him diagnose the entire car.

RE: C320 Battery Replacement Problems
 

Had same problem with my 2001 c320
purchased new battery but it would be dead if I did not drive it every day.
Took it to dealership and they found that the power seat was draining the battery.

Replaced power seat control module...final cost ~555.00
did anyone else have the same problem??

RE: C320 Battery Replacement Problems
 

Hi Alkir:

Yeah, the new battery is practically dead if you don't drive the car thoroughly. That happened to me after I left my car in the garage w the new battery for a week. You have to drive the car to charge the battery. Then its fine.

I had the exact same situation as you. Just got my C320 back from the dealer for a diagnostic ($130 for 1 hour). They said the "Seat Recognition Sensor" (the same SRS airbag message that I can't get rid of) "coincidentally malfunctioned at the same time when the battery went dead. It cannot be fixed or reset and needs to be replaced. They quoted me $530 for parts and labour. I gave the part description and vehicle identification number to my mechanic friend. He will do the job for $350 parts and labour.
Always check to see if you can get your local mechanic can do the job first.

RE: C320 Battery Replacement Problems
 

I am having this exact Battery Drain problem right now with my 2002 C32 I bought a few months ago. If I don't drive it within 12 to15hours the battery will be dead as a door knob. Sometimes when I jump it off and start driving the transmission will not change gears. Usually I drive it enough for the battery to recharge then I turn the ignition off and back on and everything is OK. A local non-dealerMB shop troubleshot it for 2.5 hours but could only verify a 1.2 amp draw from an unknown source and that I would have to take it to the dealer to be troubleshot for $205/Hr. with a 2 hour minimum. One night sitting in my vehicle it sounded like a hum was coming from the SOS console. Do you reckon I have a power draw from the seats as well or a bad light bulb? HELP!

bigbus920

RE: C320 Battery Replacement Problems
 

bigbus920:

I think the best thing to do is have the M-B dealership identify the problem for you. Yes, it will cost some $ but at least you will have on paper what the issue is. Its better than having a non-dealer mechanic "guess" the issue and fix the wrong issue.

Your M-B seems to charge too much just for troubleshooting. My dealer charged $130/hr Cdn and did the inspection in 1 hour.

Once M-B has identified the issue, you can have a non-dealer mechanic order the replacement parts and install it for you at a lower price. In my case, the issue were the two power seat sensors (drivers and passengers) which were sucking up the electrical power - even when the car was off.

RE: C320 Battery Replacement Problems
 

You're probably right. That's good advice. I should probably travel to the next nearest dealership to get a better price for the troubleshooting. Thanks!

RE: C320 Battery Replacement Problems
 

morning! your car does have battery drain issues with the seat control modules under the seats if they have a part # starting with 203 then they need to be replaced with the part # that begins with 211. you might be able to see the part #'s if you look carefully under the seat and maybe with a mirror. as for some of the errors and issues you are having you wipers and washers, theyshould work regardless of battey dying. sounds to me that there is another issue with your car other than the battery dying.

RE: C320 Battery Replacement Problems
 

I also have similar problem on my C320 2003. My batery died after returning from 1 week long vacation.
I bought new batery. Now my driver seat doesn't work. After I open the fuses and just take them out and put them back my seat works again. If I leave my car off for couple of hours my seat doesn't work again.
What could this be?

RE: C320 Battery Replacement Problems
 

fifan

I finally spent some quality time to explore my problem and found two connectors under each seat and disconnected them and now my battery does not lose power. Apparently the seat module needs to be replaced because I pulled fuses 1 and 2 in the trunk and the seats just kept working. It took the better part of 15 minutes to find the connectors and disconnect them.

RE: C320 Battery Replacement Problems
 

I have a C320 2002 and my battery recently went dead. The mechanic replaced the battery and reset the electronics for $250.

5 days later the car was dead. The mechanic diagnosed the problem, and changed the seat control module (front passanger) for $866 parts and labor. Just received car, everything seems OK.

He said the module was $410 and all else was labor and diagnoses. Is this reasonable?