So, new to me, 97 E300 D. Came with 2 keys, only 1 works. Can't find a lot of info about them, other than it's an infra red system as opposed to radio freqs (i think). Ignition key looks like a pretty standard, cut metal key. Flips out from the fob like a switchblade (sorta)
Is this remote (locks/unlocks doors) a dealer only item for replacement? Is replacement even possible?
Thanks

I assume you've tried the easy stuff like replacing the battery? Yes 97 key is IR and requires line of sight, like a TV remote.

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Current fleet:
1998 E300 turbodiesel
2008 E320 bluetec - leaky oil cooler seals replaced
2012 S350 bluetec
2014 GL350 bluetec

Sold:
1996 Passat TDI
1997 E300 diesel

Yep, did the easy stuff. The non-working remote is a little beat up (compared to the working one). Took the circuit board out and examined under magnification. Didn't see anything obvious. Also, using a cell phone camera (or any digital camera, I guess) you can see the remote emitting infra red light when the button is pressed. The "good" one and the "bad" one.
Haven't contacted MB, yet, to see how ridiculously expensive they are. Or, if they're even still available....

Ok, finally made it to my local MB dealer today and inquired about the availability of key/remote for the '97 E300 D. The key/remotes are still available I was glad to learn. Kinda good news as my newly acquired W210 only came with 1 working remote (2 keys).
The working one is a little beat up and the non-working one is totally beat up. Don't know why it's not working. It's all there and looks ok. I only know the remote door locks use infra-red and the key case has a "chip" in it for the security system. Beyond that, I'm at a loss.
Conventional wisdom dictates 2 working remotes/keys and I'll feel a lot better when I have 'em.
When new, the car also came with a valet key (only operates passenger door lock and steering lock??) and a "flat key" which MB suggests you keep in your wallet. Neither of which will "start" the car, I'm guessing?
I miss the days of plain old keys......