Keyless entry ("KE") to my 1995 E300 is finally complete. This is not so much a "DIY" as it is a "here's what I did." I can provide more details if anyone wants them. Specifically designed for model year 1990-95 W124s (those with the "convenience relay" under the rear seat), pieces of this thing can be used on any 124 and probably other M-Bs as well. YMMV as usual.

This is a complete system -- it may do more than you want. Features:

• All key-operated functions are duplicated with the remote. Key and remote can be used interchangeably. The "KE" electronics occasionally gets lost if you mix/match but re-sync is easy by pressing the opposite button.

• Central Locking is also available from a console-mounted switch, which duplicates the function of the door buttons. (This console switch, like the door buttons, does not arm the alarm.)

• "Convenience" closing of all windows and sunroof is available with the KE remote; its use is the same as it is with a key. This is a complicated system with a long list of what it will or won't do and I still haven't figured it all out.

• A security switch disconnects the driver's door from Central Locking. This allows the driver to lock or unlock his door with the key or with the door button without locking or unlocking any of the other doors. Complete locking/unlocking is still available with the console switch or with the remote.

Wiring diagram:





Electronic bits, under the rear seat next to the Central Locking pump. When this picture was taken I hadn't run the wires under the carpet to the switches in the console. This under-seat location makes it easy to connect to the "Convenience Unit," on the other side of the seat, and through it to the alarm.





KE remote and the added console switches. The Central Locking switch is a window switch with the up/down arrows blacked out -- alas, the factory switch doesn't have the right pin-outs for my circuit. My car's console has the optional "limo wood" panel (124 683 38 37) with all of the switch holes punched.





Details? Just ask!

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970