Periodically, the Harmon Kardon radio that came with car will turn on. Car is turned off, no key in ignition. Radio not left on (not that that should matter). Drive somewhere, go inside store or arrive home and come a little later and radio will have turned on. Once it totally drained battery overnight. Any idea what can be causing this or how to fix?

 

Thanks. I will note that you can turn the radio on when the car is off (i.e. no key) so the radio receives power all the time. I was planning to pull the fuse tied to the radio and confirm that there is no further battery drain ... temporary fix.

How do I look into the other issue you suggest: the ignition and/or central gateway module?

 

You should visit the 211 forum, which is what your car is. Maybe others there have had the same issue. Regards. Ned.

 

Hey VirginiaE20. Welcome to the forum...I see that you are also from VA...what part? Sorry that you have this issue, I had a similar problem with my e39 BMW in that the entire HVAC system would turn on by itself overnight and blow at full speed! Car was bat-sh** crazy.

Sorry, Plutoe, but you are also confused...VirginiaE320 is indeed correct, in that the radio will function with the car off and no key. They have been doing that for years, both Mercedes and non-Mercedes cars; sometimes when I am washing my car or out in the garage, I will reach in and turn on the radio to catch some tunes while I am doing a small chore---no keys or ignition required.

 

I've had the radio come on while driving without touching a thing. Just passed it off as one of those quirks my LEMON does.

 

This indeed correct. I listen to the radio all the time with the ignition in the off position after I park. It will continue to play till you open the door or till the battery minder turns it off (20 minutes or so).

 

Even more odd that the OP's radio kept on playing until battery was flat. If it turned on, the 20 minute timer should still have saved the battery but that did not happen.

These modern head units tend to reset every now and then, some more often than others. Could be it does not remember the on/off state after a reset but if the car had been parked, the radio should not be active at all to make any resets (while driving the radio control unit is active even if the driver switches the radio off).