My alarm sounder (the chirp on lock/unlock) has recently been getting quieter and is now barely audible over the sound of the locks themselves. Haven't had a chance to pull it to inspect yet, but I figured I'd look in the electrical guides to get an idea of how wiring is set up for it. The index shows it should be in diagram 13.3/13.4 but that one's omitted from all the PDF's I've found (I'm guessing they were omitted so that people can't learn to bypass the car's security system). I didn't see it in the large files section or on jagrepair... anyone have the diagram? (or thoughts on what to check, aside from obvious corrosion/grounds/connections?)

 

http://www.jagrepair.com/images/Auto.../jagxj1999.pdf

See page 53 , maybe the BCM " case " ground , easier said then done .

Are there 2 sounders in the cabin ?

 

Below is an old post reply of mine for the sounder. They are replaceable. The batteries are not. They are rechargables that are in a potting compound. You have to dig them out. to replace then you have the problem of sealing them back up. The dieing batteries are the problem. They normally recharge during running so that even if power is cut the alarm will sound.
There is a lot of info for determining if your sounder is and active or passive sounder. There is a big difference in cost.

https://www.jaguarforums.com/forum/x...arming-166087/

 

So they won't make sound if the internal battery is dead, even if the car's battery is hooked up and charged?

 

They do make sound, in most cases at least.
Mine does, as long as I have the car battery hooked up to it.

Problem starts when the batteries start to oxidate, they can cause the battery to drain among other problems.

 

The weak sound you are getting is the cars battery powering the sounder. Once the batteries get bad enough to no longer make a circuit the sounder stops. You will only have the lights flash and no sound.

 

That makes sense, I was missing that the sounder battery would be wired in series with the circuitry. I'll look into a replacement part then, or maybe dig apart the potting if it looks doable.

 

No luck on anything so far. Mine is a passive sounder, 2 leads. No batteries in these, even dug one apart just to be sure. I picked up a spare from the junkyard and it also didn't work. No sound at all from any of them. If I poked at the 2 pins that are used on the sounders with a low-voltage power source, it made clicking noises, so the passive sounders are probably just a piezo or speaker with nothing else going on. Impedance measured ~7.5 ohms on the junkyard one so it is probably a standard speaker.

When trying to read the voltage off the pins while locking/unlocking the car, I would occasionally get blips of maybe 1.5v when the sounder would normally chirp, which is about what I'd expect to get off a chirping signal going to one of these. My multimeter leads were too big to fit into the connector so it's hard to know if the inconsistency was from poor connections there or an issue in the car itself. I tested the impedance across the pins and got no conduction at all. The only easy thing I'm realizing I forgot now was to test for a ground fault... I even tried plugging in a standard speaker to see what would happen, and still no sound.

I'm not really sure what else could be going on, unless the BPM is faulty, or there's an issue with the wiring between the BPM and sounder. Ran out of daylight today, so on my next free day I'll pull the splash shield in the wheel well, and test the BPM pins. I still can't find a electrical diagram with figure 13.3 in it, that seems to be the one that would have the wiring for the sounder. The closest answer I've found is this thread https://www.jaguarforums.com/forum/x.../#&gid=1&pid=1 which hasn't gotten me much further, except for maybe pin numbers to test on the BPM harness.