Check Your Alarm Backup Battery and Auxiliary Sounder

Rather, disconnect it. The unit is way too old, and the rechargeable cells inside are depleted. It is located in the Right, front wheel well, roughly under the headlamp assembly. It is a square black box. Not necessary to deactivate it in IDS, just disconnect, seal and stow the connector in some efficient way.

This can cause all sorts of weird little problems. Something which has perplexed me for a few years is that the battery level indicator on my battery tender harness would shift from green to yellow overnight, a slight drop. Did not do damage as i was always very careful to place on the maintainer after every drive. Now, with this unit disconnected, the now older battery stays at full voltage for days without being on the tender and in a hotter climate. Did an A/B test and can make the problem reappear.

Since this unit might develop an internal short it can also cause issues with other things by both loading the alternator at idle and dropping voltage to various modules. It used to cause an intermittent idle drop when coming to a stop. Once again, A/B test can make it come back. It also messes with Real Gauge at idle and causes a reset of sorts. Thusly, mine has some sort of intermittent internal short.

Your factory alarm will still work the same way absent the various chirps if you have something open while active arming or the indicator chirps if enabled in IDS. There is of course no backup for the horns or if the main battery is disconnected.

I have/had? an occasional ECU error on startup if the vehicle was parked outside in strong winds. Would clear on restart. Don't know if related to this unit, however will one day find out.

One wonders how many odd problems this unit has caused for others...

 

Last year in may (2023) I bought a used, two owner 97 xk8 coupe(USA left hand drive)… while sorting out a bunch of various issues I came upon the realization that this alarm module you speak of in the (for me) passenger side wheel well was not only disconnected, the module was completely MIA. I bought a used one on eBay, a “passive sounder” and plugged it in, and locking the car with the fob it chirped, but I have not installed it for good. I wasn’t sure if my car originally came with the passive type or the (I believe) “active” type, or even one at all. I don’t care for the chirps much, as my car stays in a locked heated and air conditioned garage, so I don’t even lock the car when parked. I do notice odd behavior sometimes when locking it with the fob when going places, sometimes it works, sometimes it don’t, no chirps obviously, but other than the occasional store, it’s either parked in my garage or it’s at a car show with key in ignition and windows open. I also find myself wondering what other issues it may cause not being connected. I can leave my car untouched for a month and it’ll start right up, but while working on it recently I left it untouched for a month and a half with the hood open and battery was runndown enough to not start. I also just recently installed real guage system for coolant and oil pressure so I’m glad you mentioned that. Again I rarely lock the car as it’s in the garage or at a car show, or I’m driving it. When I run in a store for a few moments I don’t bother locking it, as in my area I doubt anyone has the know how to even steal it, given the odd key. Most people pay no mind to it or stare at it and ask me wtf it even is lol! I recently had an older lady stop dead in traffic heading opposite way as me and told me it was beautiful, and asked me if it was an xke… I was flabbergasted and told her she was on the right track but a few decades off, that it was An xk8, and I think I blew her mind! Thanked her for the compliment and told her if I ever saw her out doing yard work or something I would take her for a ride!!!! I recently went to a local car show with about 300 cars and I had the only jaguar there, but most didn’t even know what it was, even had a guy ask me if it had a v12 in it, my reply; I WISH!

 

It's a real shame that they gave no thought to future maintainance on these alarms, as those batteries were always going to die at some point, even if it is well after the original warranty has run out.

 

Really cannot pin any blame as the units worked for a very long time. One of my friends ground out the potting material and attempted to change the cells, however there was other damage in the unit, thus discarded.

For the other poster, there is no issue removing the unit. It was an optional item and not necessary for anything else other than what i described above.