Not too much of a problem as I'd always wanted to replace the system as the range of the old one was quite limited.
I had bought a keyless entry system from Aliexpress since 2 years ago and had no good reason to install it until a week ago when it rained so heavily that it shorted my siren +12V wire to ground and rendered the old keyless entry system useless.
http://www.aliexpress.com/item/Free-Shipping-CF904-Keyless-Entry-Car-Alarm-System-With-Flip-Key-And-Logo-Trunk-open-function/493509728.html
This was the system that was purchased and the instruction manual looks like this.
Honestly, even for an electrical engineer, the instructions were quite useless...
Then I found help,at Peachparts forums, where many classic Mercedes owners, contribute technically to helping other owners, in this thread.
http://www.peachparts.com/shopforum/diesel-discussion/283569-diy-keyless-entry-door-lock-w126-w124.html
They were using the same system and one of them had the proper wiring instructions.
The wiring colour code was exactly the same on my module [ Left side ].
The only problem now was to look for the corresponding signal wires to tap on the car itself
[ie door lock/unlock, blinker ]
Lucky for me, my old keyless entry system, had the required wiring already brought to the front [ under dashboard ] where the door, turn signal blinker and siren wiring, was already on the connector of the old keyless module. And because I had the instructions and wiring diagrams for the old system [ handed over by previous owner ], all I needed to do was to snip the required wires from the old connectors and connected them to my new module wiring.
