I've got two folding infrared keys for my '92 300SD. The one I use all the time seems to have gone inoperative. I know it is generating infrared, but doesn't seem to operate the locks. I(I have new batteries in it.) The other key works but has the loop on the non key end cut off, so I can't put it on a keychain. Does anyone know how to take them apart so I can exchange the guts?

The origional key was huge, the second key was smaller, and the third had a key loop. I assume you have tried to sync the key aim at handle and then lock and unlock the doors manually.
The remote halves snap together, you will have to examine the spring layout

Attached Files

Infrared.pdf (38.3 KB, 133 views)

Thanks for that help Peter

I got the key apart and found that there is a microswitch in there which is activated by the large push button. It had become disconnected from the circuit board. Puting it back together was not particularly difficult—just be careful of the spring which flips the actual key. When I soldered it back on, and synched it up again, it works fine!