I just bought a used 2001 C320. I feel foolish but I'm having trouble with the locking system. Sometimes the key locks the car, sometimes it doesn't. While at the dealership, it did the 40 second auto locking thing but now it won't. The key light blinks when a button is depressed so I assumed it wasn't the battery but could it be? I have read the owner's manual regarding the locking system but I just can't seem to figure out what I'm doing wrong.

 

Hi,
Quote:....Sometimes the key locks the car, sometimes it doesn't.

Are you referring to with the KEY or the REMOTE?

Auto Locking is a programmable feature. Maybe you have unprogrammed it somehow.
Try pressing the Lock/Unlock button on the dash for 5 secs or so. What do you have now?

Does the car currently lock ("clunk") at about 5mph?

 

Yes, it locks at 9 mph like it supposed to, and yes, with the remote. I got stuck in a parking lot today, car wouldn't unlock until about 5 presses. I was in and out of it today about 5 times and it worked everytime except that once. I will try the button on the dash.

 

I'd try replacing the battery in your remote.

 

I will do it and see what happens. It did something funky today too. I was parked...got in and started it and put it in drive and the passenger side mirror when wacky and started moving, tilted itself all the way down. Oh, and the car won't do the windows and sun roof thing when you hold the unlock key down. That might be a battery thing too.