I guess it is time to give back a little since this forum helped so much with getting my w124 up and running.

There are numerous threads about installing keyless entry devices on our cars. There are many different ways to do it. I am only showing how I installed this particular keyless entry system into a 1994 E320. While all the installs are very similar, there are differences between model years and by brands of keyless entry systems. So all of this only applies to the Docooler Keyless entry as installed on a 1994 E320. It will likely work for many other MBZ years/models and I will try to explain where it may be different. All this does is unlock and lock your doors and gives you a visual flashing at all 4 corners so you know it locked/unlocked.

First - here is what I installed (about $18 on Amazon) The instructions are awful, but it is cheap and works:
[ame="http://www.amazon.com/Docooler%C2%AE-Central-Locking-Keyless-Controllers/dp/B006QH9C5A"]Amazon.com : DocoolerŪ Car Remote Central Lock Locking Keyless Entry System with Remote Controllers : Vehicle Alarm Accessories : Electronics@@AMEPARAM@@http://ecx.images-amazon.com/images/I/51PvGeJj89L.@@AMEPARAM@@51PvGeJj89L[/ame]


Like many, I used the wiring diagram provided on Peach Parts to help. But it wasn't complete and I had to make a change. The attached image shows the changes I made.

For my install, I decided to attack at the vacuum pump. I did it there because you will find constant power, ground, and access to the control wires for your locks (DS door, PS Door, and trunk). You will need to pick one of those wires, and whatever you pick will need to be in working order. In other words, don't pick the trunk wire if the actuator is bad. I chose to splice into the green wire for the PS door.

If you remove the rear seat bottom, the vacuum pump is on the passenger side inside a foam block. You will see two plugs attached - a round one and a flat one. You will tap into power and ground at the flat plug. The red plug wire is 12V and the brown plug wire is (there are two brown wires going to the same pin, use either) for ground. The Docooler vice needs 12V to the red wire (device power) and to the Yellow/Black wire. It needs ground to the black wire (device ground) and the Yellow wire. (Note this is where the Docooler is opposite from many other devices with respect to the Yellow and Yellow/Black wires. If you wire it like the Peach Parts diagram, it still works, but the key fob buttons work opposite - lock button unlocks and vice versa). I found it easiest to join the red and yellow/black together and then splice the combined wire into the red flat plug wire. Same thing with the Black and yellow wires, joining them together before tapping onto the brown plug wire.

Next, you have to decide which lock wire you want to splice at the round plug. Green is PS Door, Yellow is trunk, and Blue is the DS door. You can pick any one of them, provided that particular lock is functioning. Snip the wire and connect the white device wire to the side closest to the plug. Connect the Orange/Black device wire to the end going into the harness (i.e. toward the lock). (Note: some MBZ models have a 6 wire round plug with two of each color. In fact, my E320 had that plug tucked under the pump. If your car has this setup, I believe the install is the same, you just need to find out which of the two wires carries 12V when activated - or try both)

The next step is to combine the orange and white/black wires together from the device.

You can be done at this point and tuck everything under the rear seat bottom and it should work fine. The only problem is you have no signal that the car got the command. In addition, if you keep the device under the rear seat, you are likely limiting the range.

So here is what I did. I mounted the device to the underside of the rear deck in the trunk (3M dual loc tape). I fed the device antenna up through one of the holes in the trunk and taped it to the underside of the speaker shelf. This way I have the antenna relatively high and not surrounded by metal. Not sure the range, but it is at least a hundred feet.

In terms of signalling, this is where you use the brown wire from the device. When the device gets a signal, it sends a couple 12V pulses through the brown wire. You can decide what you want those pulses to alert (horn, various lights). I wanted a silent signal visible from all 4 corners, so I went with the running lights. I ran the brown wire to the PS rear corner and spliced into the Gray/red wire to the rear tailight. Find the harness and cut back the sheathing, and connect your brown wire. You only need to plice in the one corner, but it lights up all 4 corners.

The Docooler device also has a red/black wire to pop your trunk. But since our cars don't have this feature, you don't use this wire.

The last step, when everything is plugged back in, is to hold the little white "learn" button on the device and press the lock button to link the FOB to the device.

In order to locate the device to the rear deck, I did have to extend the device wires and I had to extend the brown wire to reach the rear corner. As stated earlier, you can just shove everything next to the vacuum pump if you want to save time.

This install took me a few hours, but only because the directions were awful and it was a different from other installs. But if you simply installed at the vacuum pump and didn't remote the device anywhere, you could do it in an hour. Even remoting it, I could certainly install this again in about 2 hours since I wouldn't have to re-figure out the wiring.

I will try to add some more pictures to clarify this long-winded post. but hopefully it helps. best $20 you can spend on your car IMHO.