DIY Keyless Entry on a W126 - PeachParts Mercedes-Benz Forum

project84300sd · #1 05-03-2009, 08:29 PM

Parts Needed:
1. DIY Keyless Entry System From Bulldog - Available at Pep Boys for $30

2. A2C Model 742 Power door lock Actuator - Available at Pep Boys for $12

3. 14 gauge wire ~ 10 feet

Tools Needed:
Phillips Screwdriver
Wire Cutters
Electrical Tape
Metal Hanger (for pulling wire through door jamb)
Power Drill will 3/8" or similar drill bit

I did some homework prior to purchasing a key less door entry system. I found the Bull dog key less entry system to be a good balance of quality, cost and ease of installation. In addition, the system comes with a lifetime warranty. Total installation time is 1.5 hrs max, with this guide, maybe 45 min.

1. Roll window up. Remove the drivers side door panel. You can search for more detailed posts on how to do this but you basically need to do the following:
a. unscrew door lock knob
b. unscrew lower screw on door handle and the screw on the center support of the door handle
c. carefully pry plastic cover behind door handle and remove small screw
d. carefully pry plastic cover trim around door handle down to expose large screw that hold the top of the door handle to the door
e. remove door handle
f. carefully pry off seat control switches and underlying plastic trim
g. remove two screws located on chrome trim surrounding door latch mechanism
h. reach under door and pry plastic cover for courtesy floor light off. Pull light assembly out and remove assembly by disconnecting the two plugs

At this point you should be able to slide door panel up and off the door.

2. Location of power door lock actuator:

You will need to remove the plastic tab that resides in this location. Cut the small portion of metal that is recessed so that the actuator can sit flush against the inside of the door. Use the image above as a reference to where to drill the holes. This does NOT have to be exact because the rod that is attached to the actuator allows for a degree of flexibility. I recommend you place the actuator on the outside of the door, mark your holes and drill. Slide the actuator behind the inside of the door and feed the mounting screws through the hold and screw them down. THIS IS NOT A TIGHT FIT, you have plenty of room to mount the actuator.

Put some paint on around the screws and the portion of metal that you cut out so that it doesn't rust. I prefer POR-15.

You will see that the power actuator is connected to a metal rod about a foot long. You need to feed this rod up through the door so that it is parallel to the metal rod that door knob screws into. IMPORTANT: feed the rod up through the door inbetween the inside door and the vacuum door lock mechanism. This is the ideal path for the door lock actuator so that it does not bind with anything.
See Images below.

NOTE: you may have to bend the metal rod (last 4 inches of the rod) of the aftermarket power door actuator. Basically it is one 90 degree bend followed by one more 90 degree bend. You will see what I am talking about when you install it. It is VERY straight forward and easy. The aftermarket power door lock actuator rotates where it connects to the metal rod which allows for a GREAT deal of flexibility. The whole point of making these bends is so that it is easier to join the two metal rods. See picture:

The two rods join together with a metal bracket that is supplied with the kit. VERY STRAIGHT FORWARD. Note the two 90 degree bends I made to the aftermarket power door lock actuator.

You are now done with the 'hardest' part of this install.

There will be two wires coming out of the power door lock actuator. You will need to use your wire and electrical tape to extend these wires long enough so that they will reach through the door to the space underneath the drivers side dash ~ extend the two wires approximately 4 feet each to be safe.

Next, remove the carpet door kick panel next to the emergency foot brake so you pull your wires through. To do this, you will need to remove the two screws that hold hood release handle.

Once the panel has been removed, drill a small hold about an inch above two holes that the hood release latch mounts to. Again, this doesnt need to be exact but just slightly above these two holes.

Once you have drilled this hole, feed the metal hanger wire through this hole, THROUGH the holes in the door jamb and into the door. This is NOT hard BUT take care to not FORCE the metal hangar wire through. This part will take patience. Once you have feed the metal hangar wire through tape the two wires from the power door lock actuator to the metal hangar wire and GENTLY pull them back through into the drivers side footwell.
See images: NOTE* image shows wire already pulled through and door panel reinstalled (forgot to take pics)

A shot of the wire through the door jamb:

Now follow the above instructions to remove the door panel in REVERSE order. You are done with the door portion of this install.

At this point you basically need a good location for the Ground and feed one wire through the firewall to the Positive (+) of the battery.

Lets begin with running a Positive wire (+) from the battery. This part literally took me 5 minutes. NOT hard at all. There is a huge hole already in the firewall where the fuse box under to hood feeds through. If you pop the hood and look behind fuse box, you will see a rubber tube that feeds all the electrical wires into the cabin.

Open the Hood of the car. Remove the fuse box cover located next to the brake booster. Look underneath your dash (drivers side) and you will see light coming through the location where the wires feed into the cabin.

At this point, DISCONNECT THE CAR BATTERY if you haven't already done so.

Tape wire to one end of the metal wire hangar and carefully push it through the hole in the firewall and feed the wire into the fuse box.
See image: (sorry not clear but you will see what I mean - VERY EASY)

Once the wire is fed into the fuse box, I pushed the wire through once of the existing empty rubber grommets located on the side of the fuse box. (A VERY CLEAN LOOK) See Image:

Once the wire is fed through, route it through the engine bay carefully along the outer heat panel to the battery.

YES, I know that battery is way too small for this diesel but I plan on changing it really soon!

Now its just a matter of connecting the Positive (+) wire to the Keyless Entry Unit. Also, there a few nice big bolts on the inner footwell where you can get your ground from. There is plenty of room under the dash to mount the unit so choose a place to your liking.
Follow the wiring instructions provided with the kit. VERY STRAIGHTFORWARD.

Reinstall the panel and double check everything.
ENJOY YOUR KEYLESS ENTRY. I will add instructions later to wire a relay so you can have parking light confirmation. I chose not to purchase the relay due to a lack of funds and time.