New Key Synced - Old Key Now Stopped Working?

[davidduk]

Hi

Can anyone help please?

I picked up a brand new ignition key for my 1996 C180 W202 today from Mercedes main dealers.

I drove to the main dealers using my old key. Once there I locked the central locking system using the old key. The old key has been locking and unlocking the central locking system perfectly. At the dealers the new key was synced to the vehicle and as expected worked first time. I drove home and locked the central locking system with the new key and then I left the new key in the house to use as a spare if needed.

So far so good. I went back to my car and went to unlock the central locking system using the 'old key' (that was worked perfectly before even while I was at the main dealers 30 minutes earlier) but now it would not unlock the central locking system. I had to get the new key from indoors and I tried that and of course it worked perfectly. So I now have a new key that unlocks the central locking system but my old key won't (I've tried re-syncing the old key but it doesn't want to know).

Question: Is this what happens when you sync a brand Mercedes Main Dealer key to your vehicle? In other words, once you have a new key from the Mercedes factory does the the old key become obsolete (to do with the programming of the new key perhaps)?

Or... is it by some amazing coincidence that my old key that was working perfectly well when I arrived at the main dealers suddenly developed a fault on the 20 minute drive home, even though it wasn't being used?

Note: The batteries are fine, brand new quality batteries fitted a couple of weeks ago and working without a problem ever since.

Thank you

 

[Blobcat]

Not sure which key you have but Mercedes can remove keys from the system. There is a limit to how many keys are active and they can disable keys.
Worth a trip back to the dealers and ask them if they disabled any keys when they coded up your new one.

 

[davidduk]

Hi @Blobcat - Thank you for your response. That's a great thought (re disabled key). To add to the mystery I forgot to check the emergency key and pad earlier (that little flat black plastic rectangular device with a central locking button and integral blade key). Just tried it and that works but the old key still not working. As you say worth a trip back to the dealers. Thanks again.

 

[Botus]

anything in the book?

on most brands you must have ALL keys present when you add a "new" key, I think the idea is you resync all keys at the same time... if you don't u get the issue you have

most cars can be done by the user at home, using some odd sequences to set the car up in learning mode

 

[davidduk]

anything in the book?

on most brands you must have ALL keys present when you add a "new" key, I think the idea is you resync all keys at the same time... if you don't u get the issue you have

most cars can be done by the user at home, using some odd sequences to set the car up in learning mode

@Botus thanks for your reply. Something weird is going on. The young guy at Mercedes gave me the key and asked me to try it. I don’t think he knew about syncing. So I synced the key (2 second job) while he watched. Perhaps there’s something else that needed doing at that point. Anyway I’ve since spoken to the parts manager whose been there for years and normally knows his stuff. From my explanation he’s puzzled too and asked me to take the car in and someone will have a look. So fingers crossed.

 

[Botus]

maybe there's a method to replace a key and he should have used add a key ?