www.jec.org.uk

Just posting this as may be useful for others. The battery on my 98 XK8 seemed to be draining, throwing up fault codes. I knew the battery was ok as it was replaced last year. After some research, I discovered a series of you tube videos entitled ‘secrets of the xk8’ (fascinating stuff, I am hooked on them now!). It mentions the ‘intelligent sounder’ as a possible cause of battery drain. This is what chirps when you arm or disarm the car and is a battery back up alarm. Mine has never chirped so I assumed it was dead. Apparently it has built in rechargeable batteries, which after 23 years are bound to have failed. However the car battery keeps trying to recharge it, hence the battery drain. It can also cause false alarms, apparently. It is situated beneath the drivers side wheel liner, pretty easy to access. So I have taken it off (it’s not essential to the alarm), hopefully will cure my battery drain. They are hard to come by now, but Eurojag had one for £51. If the battery drain is cured then I shall fit the replacement and we shall see.
Thought may be of use to someone.

It is a well known problem within Jaguar circles. If you do replace it and the chirp still doesn’t work then it will require “switching on” via a diagnostics machine.

I would also check the flap in the ignition barrel is closing when the key is removed.

Will do, many thanks.

The earlier versions of this alarm have rechargeable batteries similar to standard AA size batteries. The space in which they're fitted in the sounder is filled with a bitumastic type substance making the removal of the batteries virtually impossible. The later models have banks of rechargeable coin cells that can be replaced quite easily, but having done that I still got no response! Time was against me so I never followed it up to try and resolve the problem and it's caused me no problems. Maybe this Summer

Yes, I took it apart just out of interest, apparently it is a 7.2volt NiCd battery pack, similar to what is used in R/C cars, widely available. In theory the batteries should be replaceable, and you could attach the battery pack separately for ease of replacement in future. Might try it just to see if it works..

Just as an update, I fitted the used one from Eurojag, still no chirping from the alarm system, so I guess the batteries on that are dead too, unfortunately. I have purchased a 7.2volt battery pack, so when time allows I will solder that to the old one and see if that works.

Keep us posted and consider taking a few pics. It would make a good magazine article for Jaguar Enthusiast. Mike.

Will do, thanks Mike

I will be very glad to be corrected (or get confirmaton ) on this, but just to say the that the siting of the secondary security alarm is quite different on the X-100 XK8s and the X-150 XKs. On the X-100 XK8s it is sited to the left of the foglamp and I believe quite easily accessed by removal of RHS front wheel and wheel-arch liner. This, like many items on XKs, (but really specific to the X-100 XK8s), is what is most often discussed and shown on You-Tube etc.

The X-150 XKs, by contrast have the security alarm located in the RHS rear corner of the engine compartment and attached to the bulkhead. You can just see it if you remove the brake fluid plastic cover at the top and peer down. Any comment as to how best to access it to either unplug or remove/replace it would also be v. interesting to know, thanks. (btw the Part No. for a replacement is C2D47174).

You are correct about the sounder's location. It's below the offside plastic cover obscured by the pedestrian protection actuator. If attempting this job, take all the necessary safety precautions when dealing with these explosive airbag style devices which raise the rear of the bonnet in the event of an accident. The pedestrian protection actuator and its bracket are held in position by 4 bolts which should be removed along with the electrical connector. Then, the two bolts holding the sounder can be accessed and loosened to release the sounder. Note that the part number quoted is only one of several versions of the sounder fitted depending upon the level of security originally specified. Eg C2D47174 does not include inclination sensing. Mike.

Tks for confirmation Mike; it's tempting (but often wrong!) to be persuaded that what holds for the X-100s will be the same for the X-150s.

The C2D47174 is the right one for the age and serial number of my 2009 5.0l vehicle, (source-Jaguar main dealer); but it does supercede an earlier quoted C2D18107, (which maybe reflects standardisation (or improvement?) to these sometimes troublesome parts).

(No, I wont be fiddling about with the pedestrian protector actuator!).

Ian

An update: Soldered the new battery pack on today, I knew it was working as the battery warmed up, indicating current flow. Plugged it into the connector behind the wing liner and.... nothing! Still no sounds, so I checked the connector plug for any current when pressing the key fob, nothing from any of the 6 terminals. Clearly the wiring loom is broken somewhere, as I would assume it should send a pulse to the sounder when pressing the keyfob button. I have already checked the 2 fuses for the sounder, both are intact. So at this point I think I am giving up and putting up with no 'chirping' from the sounder. Worth a try anyway.

Andy, did the chirp work prior to the battery failing. The alarm chirp on the XK8 is a programmable feature and can be switched on or off via the OBD port using SSD. If yours has never chirped then it may never have been switched on.

Further to JimboV8's point, this extract from my handbook suggests a possible way to force the sounder in a more roundabout fashion.

''Battery back-up sounder
On certain markets a separate battery back-up sounder is fitted. This device will sound an alarm if the vehicle battery or the sounder is disconnected when the security system is armed.
Caution: Do not disconnect the vehicle battery or sounder if the security system is armed as this will cause the alarm to sound. To switch off the alarm, reconnect the vehicle battery or sounder and disarm the security system in the usual manner.''

So you could set the alarm and disconnect the sounder, or

With the boot open, a screwdriver can be used to duplicate the effect of closing the boot lock by pushing the latch down. Then double lock to arm the alarm system and then disconnect the battery

Sadly, I can't get access to the relevant wheelarch just at the moment to try this idea out, but I'll get back before too long with how it goes for me

Thanks both, the alarm has never sounded, but the battery pack I took out from the original one was reading about 0.2volts, so definitely dead. As it was an original fitment I assume it was set up to sound. I might try the battery disconnect process and see, but with no voltage output at the plug when pressing the keyfob I assume there is a break somewhere in the wiring loom. To be honest though, I somehow doubt she will pass her next MOT in December so it may all be a bit academic!