No more horn "chirp" after doors are locked

[DPDISXR4Ti]

Has anyone else had the horn confirmation of doors being locked stop functioning? Mine no longer works. Doors lock just fine and everything otherwise appears to be okay, though I'm guessing the security horn is the same function and perhaps doesn't work either.

[Luxus Panzer]

batteries on the horn are prob dead.

Watch out for interior lights fuse blowing soon as well ;)

[old guy]

Unfortunately a common problem. The batteries go bad and corrode the circuit board. Sometimes you can clean it up and replace the batteries. I was able to resurrect mine that way. Here is a link to a TT forum but the siren is essentially the same as the A4 one. Clicky click® And another repair link. Clicky click®

[john_gonzo]

Good links above.

Remote battery packs prevent leaky batteries from ruining the board again: Alarm-Beep-Stop-Working-DIY-Fix

[DPDISXR4Ti]

Watch out for interior lights fuse blowing soon as well ;)

Thanks for the links. It never occurred tome that the siren might have it's own batteries.

But is there actually any link between the siren battery failure and the interior lights fuse?

[treysgreen]

Make sure it is detecting the doors are all closed too. I had this happen and it turned out to be a sensor in the door that detects if it is closed or not.

[DPDISXR4Ti]

I was just now going to dig into the trunk and find the siren. It would appear that if indeed it is located in the right-rear corner, the whole right-side trim panel needs to come out to get access, yes? It looks like to do that, the rubber gasket for the trunk lid need to be removed, at least partially, correct? I just want to make sure I'm digging in the right place so that I don't needlessly pull stuff apart.

[SJorge3442]

I was just now going to dig into the trunk and find the siren. It would appear that if indeed it is located in the right-rear corner, the whole right-side trim panel needs to come out to get access, yes? It looks like to do that, the rubber gasket for the trunk lid need to be removed, at least partially, correct? I just want to make sure I'm digging in the right place so that I don't needlessly pull stuff apart.

Nope. The rubber trunk seal stays in place. You just need to remove the spare tire cover, then unbolt the tie downs. You also need to remove the plastic kick plate at the back too. That has 2 bolts holding it in place and a few clips holding it down. There is also press in pin towards in the top of the trunk liner on the side. Then you should be able to get in there.

[diagnosticator]

When my alarm siren got to weak to hear, I cut the box open on the seam line and opened the box. The batteries where toast, but the circuit board was not damaged, I was able to clean it up. then I soldered wires to the battery terminals and mounted the new battery pack on the outside of the siren box. Been working good now for 2+ years since then. It is a bit tricky figuring out how the battery terminals are configured, because each stock battery has it's own terminal pair. Adding the external battery pack requires determining how the battery terminals on the board connect together, they are in series connection together, so a jumper wire needs to be soldered to the board to connect both battery terminals together so that the external battery powers the siren with the correct voltage.

[DPDISXR4Ti]

Nope. The rubber trunk seal stays in place. You just need to remove the spare tire cover, then unbolt the tie downs. You also need to remove the plastic kick plate at the back too. That has 2 bolts holding it in place and a few clips holding it down. There is also press in pin towards in the top of the trunk liner on the side. Then you should be able to get in there.

Thanks, that helped a lot. Just now got it out. Well, not fully out. The front lower corner of the panel seems to be held in place via the rear seat hinge, but with everything else loose it was easy to pull it out of the way and get access to the siren. Tomorrow I'll do surgery on it.

[john_gonzo]

Thanks, that helped a lot. Just now got it out. Well, not fully out. The front lower corner of the panel seems to be held in place via the rear seat hinge, but with everything else loose it was easy to pull it out of the way and get access to the siren. Tomorrow I'll do surgery on it.

Just in case....

Both "halves" of the rear seat backs are held in place by a curved clamp. If you fold one of the seat backs down, the clamp is visible where the two backs meet. If you remove the single bolt in that clamp, one or both seat backs can be lifted out. I think the bolt is 10mm hex head.

Good luck with the siren.

[DPDISXR4Ti]

Got the siren cut in half and the one of the batteries leaked; it "ate" through most of the solder that fastens the battery contacts to the circuit board. I could re-solder it, but it wouldn't surprise me if some of the neighboring parts on the board are fried.

I see there is an updated replacement siren, Audi part# 8L0 951 605A. I'm not sure I want to bother for now though. Is there any implications to running without the siren hooked up, short of not having a security siren? :)

[SJorge3442]

Got the siren cut in half and the one of the batteries leaked; it "ate" through most of the solder that fastens the battery contacts to the circuit board. I could re-solder it, but it wouldn't surprise me if some of the neighboring parts on the board are fried.

I see there is an updated replacement siren, Audi part# 8L0 951 605A. I'm not sure I want to bother for now though. Is there any implications to running without the siren hooked up, short of not having a security siren? :)

I've be siren-less for over a month. It would be no different than running with it without functional batteries. I would think probably better since there is less of a chance of a short occurring.

[WB650]

batteries on the horn are prob dead.

Watch out for interior lights fuse blowing soon as well ;)

The fuse in the panel near the steering wheel? That fuse works fine for me but after I unplugged my siren in my Avant for this very reason OP is having I have no dome lights.

[DPDISXR4Ti]

I unplugged my siren in my Avant for this very reason OP is having I have no dome lights.

Fortunately I seem to have no other issues. All interior lights seem to be working fine, so I suspect my siren just killed itself without taking anything else out with it. I'll attach a couple pics for reference.

Anyone have a guide on what other Audis used the same siren over what year range? With Audis of this era increasingly showing up in the junkyards, I figure I'll just wait for one that's been replaced with the newer type to show up at the junkyard.

[diagnosticator]

Even if you find a good siren in a wrecking yard, chances are good the batteries are on the way out. I don't think your original circuit board is repairable as a practical matter. If you find a siren with an undamaged circuit board, it is worthwhile to modify the siren to be powered with larger capacity external batteries. This will provide an extended lifetime before the replacement batteries go bad, and replacement of the exterior battery pack is a lot easier after fitting the siren with an external battery pack.

[DPDISXR4Ti]

Even if you find a good siren in a wrecking yard, chances are good the batteries are on the way out.

True, unless it's already been replaced with the later style and might be good for another 10 years. And with respect to the later style, does it perhaps use a battery which is still available?

I do agree that the better solution is to do the modifications for the external battery pack. Alas, as you have already suggested, I need another donor with a good circuit board no matter which direction I proceed.

[onceover]

I swapped mine with one from a B7 S4. Few years newer, should last me a bit :)

[SJorge3442]

You know, why do these use batteries? Why does the car just feed it power? can we bum power from somewhere that always has power and use it like that? I'm just thinking out loud

[DPDISXR4Ti]

You know, why do these use batteries? Why does the car just feed it power? can we bum power from somewhere that always has power and use it like that? I'm just thinking out loud

I never even realized that they had their own power source until mine failed and I started this thread. Since it's a 7.2V siren, it won't be as easy as hooking up a 12V power source from the car. But 12V sirens are readily available. In fact, best I can tell, the A6 used a 12V siren through 2004, and the B5 used the same 12V siren. As you would suspect, they use different quick connectors, but that's the least of our issues.

My biggest concern is what ramifications there might be to running a 12V siren on a system designed for a 7.2V siren. Best place to start would be comparing the schematics of the two vehicles; say, a B6 vs. a B5.

[Johann2.7t]

You know, why do these use batteries? Why does the car just feed it power? can we bum power from somewhere that always has power and use it like that? I'm just thinking out loud

to sound alarm in event of power failure (ie someone has cut your battery)

[DPDISXR4Ti]

to sound alarm in event of power failure (ie someone has cut your battery)

Yea, I assumed that's why they powered it independently; an extra layer of protection. I'd be fine without that extra layer.

[DPDISXR4Ti]

I see there is an updated replacement siren, Audi part# 8L0 951 605A. I'm not sure I want to bother for now though. Is there any implications to running without the siren hooked up, short of not having a security siren? :)

I went junkyarding the other day and found a 2004 A4 which has the later style siren I referenced above. I just now plugged it in and it works, but I figure the batteries in this one are 10+ years old, so they can't be long for this world. I'm thinking I'd rather have something in there with fresh batteries. Anyone know if this later one uses replaceable batteries that are actually available? That seems like the easier way to go if they last 10+ years.