Siren Replacement

[Willy]

Hmm, perhaps this a EU option. Our XC70 had it, there was a button in the center console to
disable it so you could leave a pet in the car while the car is locked and the alarm active.
We also had an inclination sensor and glass break sensors in the boot. The interior motion sensor
is the only one that can bes tested easily, so I tried that. If the car has this sensor and the horn
of the car sounds if someone enters the car, a main part of the alarm function is still active while
the siren module is removed.
For some reason, I can't upload attachments now. The schematic drawing of the burglar alarm
shows a CAN-bus connection between the UEM (Upper Control Module) and the SCM (Siren Control
Module). The UEM als controls the sunroof. If a faulty siren module compromises the communication
in this CAN-bus branche, it may also compromise the functioning of the UEM. That is the reason that
disconnecting the siren module can (possibly) make the sunroof to work again.

[Voldog]

...... That is the reason that
disconnecting the siren module can (possibly) make the sunroof to work again.

What I don't get is what is the difference between disconnecting (am assuming you mean unplugging) the siren module and an open fuse #38 as far as continuity of sunroof operation.

Also, I don't understand how some siren modules appear to not have fried boards and are repairable by simply replacing the batteries. Does this mean that not all boards get fried? if so, what other reason would there be for the module to go bad?

[Willy]

When the fuse of the siren module is out, only power to the module is interrupted, the CAN-bus wiring is still in place. According to the schematics, it is the same connector that connects the UEM with the SRM (Sunroof control Module) and the URM to the siren module (connecting from #21 at the UEM). If eg there is water in the siren module, the wiring of the CAN-bus branch to the UEM and the SRM will be shorted, making communication from the UEM to the sunroof (SRM) impossible. If, it this scenario, the siren module is disconnected, the short circuit of the CAN-bus branch (UEM SCM and UEM SRM) is removed and communication from the UEM to the SRM can be resumed. Unfortunately, I still can't upload attachments. If I could, the relation between a short circuit in the wiring of the siren module and the sunroof not working would become clear. I wonder if I am the only one that has trouble uploading attachments.

[Willy]

I have sent you a PM, perhaps I can send you schematics.

[Willy]

I have sent you a PM, perhaps I can send you schematics.

there is something very wrong with my browser at the moment, I have probably answerd several times to your reply of my PM. However, the answers should all say about the same (I hope). Sorry for the confusion!

[Willy]

The drawing shwows how the UEM, the SRM and the SCM are connected. You can see that, should the CAN-bus be shorted in the SCM, this would also compromise communication to/from the SRM.

[Voldog]

Another question. I see in several videos where ppl go thru removing the wheel and drilling out the rivets to remove the plastic inside the wheel well. Then they re-rivet to put it back. Has anyone ever used those push-in plastic trim/clip holders? My Hondas use those plastic clips and work fine.

[NTXC]

Personally I just used a rivet gun my dad let me borrow. I’m not sure how I’d feel about the plastic ones given I don’t have the plastic skid plate/air guide under my car.

[Astro14]

The plastic clips aren’t as strong. I just pop-riveted those liners back in. Pop rivets are a few pennies each.

The plastic clips are more expensive. I’d be curious if they hold up as well as the pop rivets, or break under use.

[Voldog]

Finally got around to checking the siren. It looks like it might be fried. one terminal on the transformer had burn marks. There did not seem to be any acid coming out of the battery. But I also noticed that 1 wire of the battery was disconnected. I got a battery from pololu that already had a connector on it. I don't know how to test this alarm if somebody can tell me I'd appreciate it I tried jumping the three prongs one after the other figuring that the battery will sound off the alarm but that did not work so maybe the board is really fried. Or I really also did not know if the alarm module has to be plugged into the car first in order to test it or powered through some kind of a car battery first. Anyway I just disconnected the alarm module for now and basically my sunroof is working again simply by disconnecting the alarm module. I took the alarm module and the metal housing out for now.