Fitting Central Door Locking to a Defender

by Espen S. Johnsen

Central door locking is one of the features in modern cars that one really can't live without, especially after first having gotten used to it. Unfortunately my 2001 MY Defender isn't modern enough to be factory fitted with this. So an aftermarket installation was definitely needed.

There are quite a few CDL kits available which are especially marketed for the Defender, such as this one from a Dutch company called British 4x4. But I just ordered a general two door kit and an additional actuator for the rear door, from Abacus Car Alarms in the UK. Total price including shipping to Norway was 84.50, which is rather expensive, but these are very high quality actuators made by MES of Switzerland and can't really be compared to cheaper inferior kits.

Front door actuators

The first step in the process of installing the front door actuators is removing the door trim casing. How to do this isn't exactly obvious if one hasn't done it before, but with the help of the workshop manual it was quite easy. I first tried to remove the studs securing the panels in two of the corners without destroying them, but gave up and just drilled them out. New ones can easily be ordered through eBay

The most obvious and probably only feasible place to mount the actuators is in the lower aft corner of the door. This position is not very different from where Land Rover has put actuators in their factory installation, according to the workshop manual. The difference being that the doors in the factory installation has been modified to easily accompany actuators, while the older doors are not prepared for this.

To fix the actuators to the doors, I used the supplied brackets and also a couple of home made ones. I wasn't completely satisfied with this, as the actuators tend to move a bit in and out when operated. Adding an extra brackets didn't help much, but afterwards I realized that fixing the long brackets vertically at the bottom of the doors would probably work much better.

This is how the cable is fed from the door. It continues behind the moulding under the lower fascia and to the passenger compartment fuse-box.

Mounting of the control relay

I mounted the control relay on the plate holding the fuses, as can be seen in the picture. Power is currently taken directly from the battery, using a cable with fuse that the previous owner had installed for some other equipment (this Defender used to be a fire truck fitted with siren and flashing blue lights and was partly painted in red). But I plan to make a more permanent arrangement by adding an auxiliary fuse box to the right of the existing ones and drawing power from one of the fuse links under the right. Another option may be to connect the relay to the same fuse as the alarm ECU (the fuse should probably be upgraded to 20 amp).

Interfacing to the alarm

Apparently the alarm ECU fitted to the Defender does not have the ability to directly interface to CDL, even if the same unit is used in other models for this purpose. It is possible to buy third party devices that could be used to do this, but before doing that I decided make some further investigations.

Just connecting to the lock/unlock pins on the external connector (pins 2 and 3 on J2) did not work, as could be expected. But when I opened up the unit and studied the PCB, it became evident that a relay (probably a EP2-3L1S) needed to control door locks was missing. My guess was that this had been omitted to save a few bucks and for the same reason, the ASIC would be identical in all versions.

The CDL relay when installed, would be driven by an ULN2003. The outputs of this chip are open collector and capable of sinking up to 500mA each of inductive load without any external components. As my CDL relay is operated by pulling the control lines low, I saw no problem connecting it directly to the outputs of the ULN2003.

After having soldered in the necessary wires, mounted the alarm ECU back behind the instrument pack and connected it to the relay, it was time to give it a try. Except first having mixed the lock and unlock signals, it worked perfectly and have been doing so for many months now.

Alarm PCB with wires soldered inAlarm after modificationAlarm PCB with wires soldered inAlarm after modification

Rear door

After having tested the front door installation for a couple of weeks, I went ahead and completed the system, by installing the actuator in the rear door.

For the 2002 MY Land Rover introduced a redesigned rear door which had among other improvements, provisions for electric door lock. The lock it self was also slightly modified for this. In advanced I had ordered one these new locks, thinking it would be easier to use than the existing. But I hadn't thought about the fact that the 2002 upgrade also included new lock barrels so that the ignition key could be used to lock the doors. Thus my old barrel didn't fit in the new lock, so I had to stick to the old.

This was probably just as good, as connecting the actuator rod to the lock turned out to be rather simple. It only involved drilling a hole through the knob meant for manual operation of the lock from inside. To mount the actuator I made a bracket of a galvanised "sieve plate" of the type very common in wooden house constructions in Norway.

I had to make a small cut in the trim panel for the rod. A custom made cover for the lock would also be needed, as the original does not fit any more because of the rod, but I haven't made that yet.

Finally the cable is fed from the door, down through the body, along the top of chassis, then through the firewall and into the passenger compartment fuse box.

Last modified 2006-10-19 21:08:35+02:00