Sunday, 17 June 2018

Swapping the 10AS immobiliser

As mentioned in a previous post I wanted to maintain factory features and factory look and feel but add central door locking to our Defender, called Fender.


To this end I have swapped the Lucas 10AS immobiliser for one that has central door locking (CDL.) This is not easy because Land Rover, sensibly, fitted this is an very awkward to get to location behind the dash binnacle.

I have used a Discovery Lucas 10AS immobiliser, which has CDL, to replace the Defender variant, which does not. By doing that I keep the standard Land Rover style 2 button key fobs (plips) and I am able to enable the same immobiliser features exactly as factory fitted.

I used a Nanocom to setup the 10AS, as noted in a previous article.


To get to the 10AS in Fender I removed the dash binnacle, disconnected the odometer cable and put the dash to one side. I'm not happy with it dangling supported by the wiring harness but I have been unable to find a better way to get it out of the way!



I also removed the small switch pod, which houses the hazard and fog light switches and the speaker below that. With all that removed I had visibility and access to pull the cables from the bottom of the 10AS.

The 10AS is bolted to the bulkhead above the steering column. There are green and grey connectors on the lower side. Each of those has a fairly easy to depress latch in the centre of the connector, facing the steering wheel. Pressing that in and pulling, with a bit of wiggle, and the connector comes out easily. The grey one is a little more difficult because it is immediately above the steering column but there is just enough gap to get the connector out and back in again.

Once disconnected I pulled both the connectors through the speaker hole.

To add CDL, I needed to connect two wires to the green connector and one wire to the grey connector.  Pins, 2 and 3 on the green connector and pin 7 on the grey connector. I bought the two different size pins from RS components.
I've already written a post detailing the connectors and pins I've used.


I wired up a short harness in the shed before starting work in the car. I decided it was easier to have a set of joints under the bonnet rather than trying to run the wires all the way to the doors in one long run. I used the wires from the Hawk CDL kit that I had bought off of e-bay. I maintained the Hawk colour coding for ease of installation. A blue and green wire, each with the larger pin to fit the green connector. A brown wire with the smaller pin to fit the middle of the grey connector.



To push the pins in to the existing connectors it is necessary to open up the connector housings. The green connector has 4 tiny plastic latches on the rear upper part of the housing. One latch at each end and another two either side of the main finger latch. A bit of poking with a screwdriver and some force got that upper part open.


The grey connector is easier, it just has two plastic latches, one either end.

Making sure the pins were the right way up, they just push in until you can hear the click of the plastic internal lock engaging with the pin. A small screwdriver sometimes helps if the wire is a tight fit.


Once I was sure the wires were in the right place I reassembled the connectors and taped the new wires to the outside of the existing cable bundles.

At this point I plugged in the replacement 10AS and attached a door solenoid, temporarily to the cables while I tested. I locked and unlocked the car, with the solenoid following as it should and I started the engine. This do not all work first time. I don't know why but it took a couple of locks and unlocks with each plip until the hazard lights followed as I had configured. It was unexpected but without making further changes, the reactions from the car settled down to what I had intended.

I removed the temporary setup before continuing.

Now for the tricky bit. Getting the previous 10AS out and the desired one in its place!

With a long number 2 pozidrive screwdriver one of the two bolts can be reached easily through the hazard switch hole.


The tricky bolt is to the left of the module. Everything is in the way. I managed to make up an extended 1/4" socket contraption with a PZ#2 bit on the end, that just reached and had enough movement to undo the bolt. Luckily neither bolt was very tight.

With the bolts removed the module can be slid to the right and removed through the speaker hole.

My replacement module had broken mounting tabs so I had the extra task of opening up the module, swapping over the internals and putting the replacement lid on the lower section of the original case. That way I got the correct stickers on the module but now with intact mounting wings. I'll be back to those in a moment.


The module goes back in the same way the old one came out. The wiring harnesses need to be pulled out the way and it took a bit of fiddling to get the unit back in place without trapping any cables. The good thing is that those cables conveniently hold the module roughly in place.

Despite the module being held up by the cables, I struggled to get the left hand bolt in to the hole with the limited space that is there.



My solution was to cut the left hand mounting hole in to an open slot and put the bolt with washer in the car first. That worked very well and made the job a whole lot easier. The right hand bolt is easy to fit and needs no such modification.

I deliberately did not over tighten the bolts.


I then ran the short harness through the bulkhead and temporarily secured along the back of the bulkhead under the bonnet.


I plugged all the connectors back in but before putting the dash back together I did a further test with a temporary solenoid hooked up. At this point, while I remembered, I swapped the remote key fobs on each set of keys and put the previous ones with the previous 10AS.

All back together, remembering to connect the odometer at the appropriate point in the reassembly.

More test engine starts, with the immobiliser activated and deactivated to ensure that everything is working as it should. The last job was to put the battery on charge to top it up after all the cranking without any movement.


Now I am ready to move on to the next stage of fitting the central door locking.

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Related articles:
https://blog.discoverthat.co.uk/2017/04/lucas-10as-connectors.html
https://blog.discoverthat.co.uk/2018/06/central-locking-poc.html
https://blog.discoverthat.co.uk/2018/07/fitting-defender-central-door-locking.html

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