Hello all and a very warm seasons greeting !!
Yesterday my door lock/security system key fob stopped working … (yes I put in a fresh battery 
)
The rest of the system seems to be still functioning normally … Central locking from the console works … and Manually operating the Driver’s door lock stem up and down also operates all the other door locks.
So is the fix as simple as replacing the central controller with an aftermarket unit and figuring out the wiring ? Has anyone dealt with this ?
My short answer is “I have no idea.”
Do you have just the one keyfob? I am assuming so being as how nothing was said like ‘the other keyfob isn’t working either’. So…your 1989 car’s remote system uses infrared to communicate. Have you checked to see if the keyfob is generating an infrared signal? Point your mobile phone’s camera at the business end of the keyfob remote and you should see a white light if the signal is being generated when the keyfob’s button is depressed. If the keyfob is transmitting the next step would be to consult the Jaguar wiring guide for outputs from the infrared receiver to verify whether the receiver generates the expected outputs when triggered by the keyfob. I think. I personally am in uncharted waters here…
Hi Mike …
When I purchased my car it was around 3 years old and I honesty can remember if it actually had the infrared security system installed (it did have the little plastic bubble on the overhead console) or it just didn’t work. Anyhow I took it to the Jaguar dealer and they must have used a newer type set up because it’s RF with the controller located under the glove box. Something like this …
I believe there is an inline fuse tucked away under there with it so as soon as I get a chance I dig under there and see what’s going on.
When I push the Fob it’s small light comes on but I don’t hear the car beep and nothing happens. So I’m thinking that It’s the control box or possibly even the Fob.
Well now that certainly changes things! If the picture you provided is like your control unit this is what you have:
Shown as being for the XJS models rather than XJ6/XJ40! This gives a clue where to look for wiring info if it comes to that.
I haven’t noticed recently but the auto parts stores - either O’Reilly or Autozone in my area - used to have on the checkout counter a device that let you test RF remotes. I assume it just checked for signal or no signal.
Grooveman, you can file this under ‘preemptive strike’. I located the 1990-91 and 1995 XJS electrical guides on Jagrepair.com and as expected, because the DAC4862 control module was shown to cover XJS’s from 1977-1996 [EDIT: s/b 1975-1996], the wiring is the same:
Note this module only services the door locks and does not provide any alarm functionality. The later (such as my 1994) XJ6/XJ40 models incorporated the central locking logic in the central microprocessor module and employed a separate security ECU module. It is a much more complex system.
Mike …
Thanks for the info, VERY helpful. Hopefully right after Christmas I’ll have the time to dig in there under the glove box and see if I can determine what’s going on.
The bummer is that if I lock the car with the key and then unlock it the alarm goes off as soon as I open the door. Of course the good news is that obviously that part of the system is working 
This is a conundrum in that the alarm system is apparently not factory OEM as it is not documented in the Jaguar 1989 electrical guide. Hopefully resolving the central locking issue - and here’s hoping that is a quick and easy one like a blown fuse - will restore proper alarm operation.
A few year ago, I purchased an aftermarket remote locking system that looks much like the one in the link you provided. I installed it above the panel in the front center of the roof liner. The panel just pries out, as i recall. My 92 did not already have remote locking but was wired for it with the connector being above that panel. Im assuming your 89 has the same setup, though I am not sure. Since you already had remote locking, you may already have a unit up there behind that panel.
