KEY will not work?????
01-02-2009, 03:21 PM
#1
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KEY will not work?????
curious iif anyone has had an issue wth one of their keys, i was able to unlock the car, but once inside the ignition there was no response from the key. My second key worked just fine. Going to dealer tomorrow, just like to ask maybe something i can do first.
01-02-2009, 04:48 PM
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2013 C300 Sport Black Darth V3.0
Batteries going? I think I remember reading it takes two lithium button cells. The key for the glove box is used to get to them it it in the manual.
01-02-2009, 05:58 PM
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C350 4Matic
Even if the fob batterys are dead, you can still start the car with the key. Of course if its keyless go you will need to pull out the button. The car is made so you can still get in and drive the car even if the fob batteries go dead.
01-02-2009, 06:14 PM
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I thought the security system had to sync codes between the key and the car before starting. Not so???
01-02-2009, 07:45 PM
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C350 4Matic
Ya this is right, but it has nothing to do with the fob battery. The key is chipped and with out any fob battery it will still start the car. Try it, remove you battery and start your car.
01-04-2009, 09:01 PM
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C300 4Matic
My Dealer told me the same thing, you can still start your engine even if the battery is dead.
01-04-2009, 10:20 PM
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Good to hear that we don't have to worry about carrying spare batteries around with us...
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01-04-2009, 10:37 PM
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2012 C300 4Matic
Actually the key is not "chipped"!
In order for the key to authenticate it needs to send an RF signal to the car as well as an IR signal through the 'window' on the front of the key. These signals "roll" each time the key is used.
There is an inductance coil in the key as well as in the dash. When you insert the key it receives voltage from the car. This means that even with dead batteries it is powered up just as if it had good batteries (as long as it is inserted).
Before someone asks where the contacts are, go read up on magnetic induction. Your electric toothbrush charges the same way.
In order for the key to authenticate it needs to send an RF signal to the car as well as an IR signal through the 'window' on the front of the key. These signals "roll" each time the key is used.
There is an inductance coil in the key as well as in the dash. When you insert the key it receives voltage from the car. This means that even with dead batteries it is powered up just as if it had good batteries (as long as it is inserted).
Before someone asks where the contacts are, go read up on magnetic induction. Your electric toothbrush charges the same way.
01-04-2009, 10:45 PM
#9
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So if the code is rolling with each start, how does the "second" key know what the code is? I am sure the answer is simple, but it seems like rolling codes would give you problems when switching back and forth with keys.
I just started my car with my electric toothbrush! 
01-05-2009, 05:06 PM
#11
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