I have a 2002 C240. And today when i locked my car. I noticed there is this red light on the smartkey that blinks when I push the lock or unlock button? Is the battery low? Or is this just how it suppose to be. Please help

 

How much does a new smart key cost? Can you just replace the battery?

 

nothing wrong w ur key. ur key works by ultrasound (locks the doors) and infrared (closes the windows). if ur windows are down and u r standing right next to the driver's door then ur key will close ur windows via the infrared by pointing on the door handle (outside) and keep it pressing.
if it won't work then there are 2 batteries in it. u can get them at wallgreens.

 

You'll know......when you need a few clicks to lock the doors its time to change the batteries. If its not super responsive its time.

Thanks for the above reply though...I always wondered why the window activation wasn't 100%. Now I know....I need to be by the driver's door!

These forums are a god-send. Thanks fella's.

JR