Having spent a while searching these forums as an outsider I have now taken the plunge and signed up.
My XJS 5.3 1989 is quite simply the most comfortable car to roll along country lanes out in the fresh air and sunshine. Its annual outing to Le Mans is coming up but there is one little gremlin which is a cause for concern.
The alarm system has lost the plot. It operates autonomously and spontaneously. Neither of the key fobs can elicit a response. The procedure to reset the alarm system is clear. Disconnect the battery and the alarm ECU power supply and then go into the reset procedure.
I cannot find the alarm ecu. It is supposed to be under the aerial motor in the right hand rear side of the boot compartment. There simply is no room for it there. I would be delighted if a member could throw some light as to its whereabouts and what it looks like.

 

@Richard

I didn't reply earlier as I have a later car and was hoping for another member with a pre facelift car to help us out, but anyway......

Glad you are having fun with your XJS. If your only problem is your alarm is not working, you're in great shape, relax, have a beer.

I have a 92 and your info on alarm location is correct....... for a facelift/after 91 car. My car did not come with an alarm but the wiring loom is all there. I checked the wiring diagrams for an 89 and there is no mention of a factory fitted alarm system...... is your alarm system an aftermarket one ? what do the remotes look like ? Do they have the Jaguar Growler on them ? or they are just your standard little black boxes with buttons? If you have an aftermarket system and it's gone on the blink, it "should" be easy enough to swap out the brain for a new aftermarket alarm......

 

I cannot help out about alarms, but are you absolutely sure it is not there? There is a huge space on the outboard side of the exhaust tunnel between it and the outer rear wing. If you pull the carpets and stuff out, and shove your head/hand into the gap, you may be surprised!

Greg

 

Thanks for the response

There have been one or two other minor problems - The power steering hydraulic fluid deposited itself on the supermarket car park, throttle pot replacement, overheating due to an air lock in the cooling system but despite these minor tribulations this car is till the most wonderful ride in comfort with masses of oomph on tap.
For a year or so I have been disconnecting the battery when not in use because I suspected the alarm system was exhausting the battery. This may have confused the logic in the alarm control module. Two weeks ago the system started operating spontaneously and emitted a couple of beeps and then locked the car. Fortunately the window was open.
I have pulled all the carpets out in the boot and stuck my head and a very bright torch in every conceivable corner. I have examined the wiring diagrams and now know the locations of a large number of relays and power failure detectors that I did not know before. There is a power supply direct from the battery to the telephone unit ( a large black box mounted in the boot on the left hand side for the brick sized telephone that were must have accessories in the late 80's)
The remote key fobs do indeed have a Jaguar emblem on them. Alas the location of the control module remains a mystery. For the duration of the trip to Le Mans the keys will be in my possession at all times.

RPM

 

Greg

Thanks. I have peered into all the nooks and crannies to no avail. If I knew what it looked like it might help. At one stage I thought the delay relay on the aerial motor was my target but after consulting the Haynes manual wiring diagrams I realised my mistake.

I shall continue my quest.

RPM

 

Yes, yes, this sounds much more like it :-)

Interesting it has a Jaguar fob..... I guess it must have been a dealer fit option at some point, although from my own experience some of the XJS wiring diagrams are completely wrong, so who knows. When it chirps or beeps or goes off, can you isolate where the sound is coming from ? Is it different from the horn ? ie a separate siren..... if you have a separate siren and can find it, tracing the wires from it may help you find the box....

Anyway, enjoy Le Mans. I've done the trip myself when I lived in the UK. Drove my Nissan 300ZX Twin Turbo all the way down from Scotland..... one of the most memorable weekends I can think of right now....

 

This is not a reply but a plea for help. I have just purchased my XJS and love it but I made the mistake of disconnecting the battery. I have read others have had the same problem as mine. Alarm beeps constantly and lights flash. Strangely the car will run perfectly with no alarm. This starts again after I turn it off.
I have tried using the key to open and close the door locks. Checked the central locking fuse,and removed the armrest tray looking for a reset connector. all to no avail.
Any help will be appreciated. Thanks Freddys

 

What year ? makes a difference ......

 

1993. sorry for the delay. I'm new on here and just trying to find my way around.

 

Ok. This works on cars up to '93. Disconnect the battery (make sure you have the radio code), when you reconnect the battery, the alarm should make a beep sound. press the keyfob button and the alarm should respond with a chirp. Do after each sound (5 of them) and the alarm will be re-coded to the fob. If you have more than 1 fob you must recode that at 1 of the beeps.
If that doesnt work you will need to reprogram for the '93 system. this is more complicated.

Recoding Remote Alarm Transmitters FAQ - Jaguar Forums - Jaguar Enthusiasts Forum

 

Well all I can say is Thank you very much Malc4d. I have been given lots of potential ways to fix this problem from other members but your way worked first time on my 93
I suppose the early days of using computers in these cars had regular updates to each model. Anyway Thanks you. Back on the road.

 

Hi again. Just thought I'd let you know that when looking for a solution to this alarm problem I also signed up to a forum in the UK, Just had a member asked where I found the info.. I hope I didn't do wrong but I cut and pasted you reply to me and sent it to him. Thanks again. Richard