Got a new flat non-remote master key from Mercedes for my '97 SL500. It works fine; unlocks, locks and starts the car. Unfortunately, as soon as I used it the original remote key would no longer start the car. It will still lock and unlock. The original remote is the one-button type. The instructions in the owners' manual seem to be for re-synching the remote to the locks, not the ignition. Anyone know how to restore the full functions of my remote ?

 

I'm not completely sure, but from a similar experience, I had to run to the dealer and have it 're-coded' to match again. They would not do it other than to have me show up with the car and my driver license and the registration for the auto. This is a safety issue as to not allow your neighbor to get a key for your car. I ordered a new key but still had the original. I wanted a spare. We stood at the dealer and adjusted both keys to the car when I picked up the new one. I'm thinking/wondering why this was not mentioned to you when you received the new one. But I'm not sure of the style of your key; mine is a newer SL so this may be a difference on the key front.