My 2009 Mercedes Bluetec original Smart Key is going bad and I don't know the reason.
As the car was bought in a small dealer from another owner it came with only one key I decided stop by on a Mercedes dealer and ask to make a new one using the VIN of the car. Dealer made one functioning perfectly. The same dealer commented with me that my original key is "almost gone" he said.
Days latter I questioned myself : "how come a key that is not a mechanical key can go bad? How come an electronic key can slowly go bad? "
I then change batteries for a fresh battery but it still with the same issues.
This is what happen: when inserting the key on the ignition it take a while to the car recognize that the key was inserted. When open the doors from outside I need to press the unlock buttons twice in order to get the doors unlocked and the same occurs to lock the doors, I need to press it twice. Open the trunk with the key is even more complicated when using the this Smart Key. The one just made on a dealer works at the first touch and the car recognize the key instantaneously.
This old key sometime stay with the little red light continuously on and then I need to open the key and remove the battery to "reset" to get it working again.
Any idea why it occurs or if it is normal to occurs with old electronic keys?
Thanks.

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Nyck - TX - USA

It's probably just wear and tear, especially if you keep the key in your pocket. Mechanical vibration, repeated use, heat, moisture from your pocket - it will slowly kill the little circuit board inside. Nothing lasts forever.

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Current stable:
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Thanks Diesel 300.
I did not think about moisture and vibration as issues. I do not keep it in my pocket but it makes sense. After this issues I keep it at home as spare using every once a while to not let it die completely.

What was the cost of the new key? Maybe you should just get another.

It's a bit odd that a key from 2009 is already going bad. Perhaps it was just faulty from the start which cut its longevity. Interested to find the reasoning behind this if you get it resolved. Thanks for sharing!

In the Dallas - TX area the cost to make a new one is $ 400.00 +
I had one made in 2016 but would like to have the old one also working properly.

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Nyck - TX - USA

I thought the same when it is an electronic device.
Electronic devices usually die completely but not going bad a little by little.

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Nyck - TX - USA

$400 - ouch.

Yes, very expensive. I try to have a local locksmith to make me one and he started cursing saying that Mercedes charge then more than $5000.00 to sell the software to other locksmiths and also Mercedes requires then to update the software every year.
He was so anger that he told me: "if people have the money, $52K to buy this car, go to the dealer and pay then to make a new key, do not come to me"
The price varies a little bit from dealer to dealer.

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Nyck - TX - USA