my battery was out today, I did not drive the car for 1 week and I got a jump start. However the problem is, when I got in to the car, the radio was on. I am sure that I switched it off, if i did not it should have switched it off by itself in 30 minutes. So any ideas how it can switch on by itself?

 

As far as I know it can't switch on by itself, on my C class as soon as you turn the "key" off the radio goes off. true it will play for 30 min or so with the engine off. My C280 has gone thru 3 batteries in the 2 1/2 years I have owned the car. too many gizmo's I guess. I don't drive a heck of a lot either. But it is also strange the radio was on when in jumped the battery. Since you jumped the battery, has the radio been on, when you've gotten back into the car after not driving for a while? Sleepwalker you have any insight on this one?

 

it can shut off by itself...yes.
the threshold (delay) time for shut off can be different according to the setting by using diagnostic computer. that is when you pull out the key and turn it "on".

turning "on" by itself is not normal. this can happen if a wake-up signal is sent through the D2B or telephone interface. was the telephone message memory full?

everytime i do the short test by scanning the control units, the radio will turn on (although it was off), which means that it can be turned "on" not only via switch... but by wake-up signal as well.

there must be an interferrence.

i never had this case before. i'll try to research for good explanation.

 

After the jump start, I turned on the radio after taking the key off and locked the car to see if it was switching itself off after 30 minutes. When I came back it was off. So there seems to be no problem in the system. C280 This thing just happened today, I will see tomorrow morning if it will be turned on by itself. I do not have a phone in the car. Thanks, sleepwalker.

 

By the way, I called the Merchelp number for the jump start and the guy said that every week there is a Mercedes in the airport that has a dead battery after staying there for 1 week.

 

battery drain was the cause.

the doesn't come into a "sleep mode" after few minutes, and continue to consume power.

the problem varies, but mostly was related to CAN (controllers area network) problem.

according to my experience, the faulty parts that continue to wake up other components are: EIS (electronic ignition switch), UCP (upper control panel), OCP (overhead control panel), interior motion sensor, ATA (anti theft alarm), and the rest are very rare.

there's a good trick in finding the current consumer... removing the fuse or detaching the CAN.

attach ammeter parallel to the battery and observe the current during sleep mode. it must not be more than 0.4 amperes.

 

thanks but I have no experience with these so I will just wait if it happens again, I will take it to the service and tell them what you have said. Usually how many days would it take the battery to be completely drained when the car is not started? And now that my battery has been drained once, is its lifetime power and quality lowered?

 

on good and fully charged battery, there should be no problem after 1 month in storage. it is said that it loses 1% of its power everyday.

once the battery has been discharged completely, it is not reliable anymore. the performance is reduced completely. i always replace a new one after complete discharge.

 

Sleepwalker, your answers bring up a question I have. my smart start has never worked correctly, the other night I turned the key 3 times before it would start. each time removing and inserting it each time. I have to Hold the smart key down in order for the car to start at time also. I've taken it to the dealer and they said it is OK? Any suggestions, as I am going in for a service soon.

Thanks!

 

when you insert the key, the data transmission between the key and EIS are exchanged to enable start. (yours is EIS?)

if not EIS, then it is the transponder which recognize the key.

sometimes, these data exchange takes time when normally it must be just in a fraction of seconds.

i have no idea about the smart key. i'll try to study that one. i heard it a few times, but never seen one.