E30 Ultrasonic alarm...

[pt///m3]

Hi,

Anyone have any insights into how these things actually work? Or how well they work? Were these a dealer installed option?

Cheers,

Paul

its the box below the climate control. The info I have on the parts are UA 201/6 CL.

[RomanDad]

I dont THINK these were an option.... Looks aftermarket to me...

If its an ultrsonic alarm, it creates a BUBBLE of ultrasonic noise in the car... Hopefully that bubble is limited to the PASSENGER compartment and doesnt extend outside the car (otherwise, your alarm goes off every time somebody walks by the car and turns into a GIANT PITA). If the bubble is disturbed it triggers the alram.

These make a LOT more sense for convertables than they do a coupe.

I had one about 10 years ago.... thing caused more problems than it was worth...

Im guessing from the looks of it, the unit you have creates 2 bubbles... Each is independantly adjusted by the screws underneath... You want to "blow up the bubble" using the screws and then test how big it is by seeing where you can put your hand before the alarm goes off.... And then turn them down to the point that the alarm ONLY goes off if somebody reaches INTO the car (Like if they reached for the stereo, or got in the drivers seat)...

Or better yet, turn it all the way down and just use a glass breakage/ door open alarm... If youre really paranoid, get the motion sensor.... but even these can be a pain.... Avoid the ultra sonic, unless you just want to piss off your neighbors.... (who will APPLAUD when they see your car being stolen, rather than calling the cops.)

[mssVT98]

I have the same one in my car, and apparently it is stock. I had gotten varying opinions on whether or not it was, but I'm pretty sure it is. You can sorta see it in the corner if this pic:



Mine's been disconnected, but I haven't gotten around to removing it yet. I wouldn't even want to mess with it active at this point.

[pt///m3]

Cool, thanks guys. I have heard that the sensitivity of these things with the windows down is way too aggressive.

Matt, if you do remove it let me know. I hear that to install that device you had to punch holes in the plastic (though some used double sided tape / epoxy) and insert screws in.

[mssVT98]

If I'm remembering right mine is mounted with screws into the back of the tray. They're so far up under the heater controls you wouldn't be able to see the holes from the seats, but it's something to consider. If I remember tonight I'll take a look and see what the deal is.

[cramer]

maybe i'm getting them mixed up, but the ultrasonic alarm sensors I thought were for glass breakage (they listen for the specific tone glass makes, you can test them by tapping your keys or something metal on the glass)

the radar sensor or proximity sensors are the "bubble" ones.

[RomanDad]

The glass breakage sensor just has a microphone of sorts that "listens" for the frequency of breaking glass.... It looks very much like those lapel mics that news reporters wear on their shirts... Mine is located above the radio, next to the rear window defroster switch. The factory alarm is USUALLY located above the glove box... Mine has a sensitivity switch for the glass breakage sensor... It was set to "low" until somebody broke my window and the alarm didn't go off... I went in and reset it to "high". Works much better now.... If I recall correctly, the BMW unit also has an extra alarm "out" plug. I have this hooked to an Alpine paging alarm which is hidden in the car along with a big ass CB antenna. It pages me if my alarm goes off so I can go out and get my ass kicked by the same guy who is stealing my car.... The range on this set up is about 2 miles....

The ultrasonic sensor is the "radar." It fills the car with a ultrasonic noise (radar) which it "listens" for and waits for the signal to be interupted by an object coming into its field... If you have a home burgular alarm with motion detectors (theyre usually mounted up high in the corner of the room and have a strange looking metalic grill), theyre pretty much the same things....

Auto Motion/shock Sensors usually have simple mercury switches of verying sensitivity that trip when the car is jolted or moved.

[mssVT98]

Ok, here's a picture of the bracket for the alarm:



There are two screws on the vertical part of the bracket that hold it on. So yeah, there are holes in the panel. I doubt it would look too terrible if you took it off though. Hope that's helpful.

Sorry I couldn't post this yesterday - my site's sever was down so I couldn't upload.

[BoxFlares]

These are OEM I had this on my old 325 back in the 90's

[pt///m3]

Cool, thanks for the picture! Definitely helpful!

Good to hear they were OEM.

[mrsha007]

bmw was on the cutting edge back then. all this combined with the evo's other features really amaze me sometimes.

[Richard]

Does a train horn in the interior of the car sound like a bad idea? I know that it is extreme, but it would sure as hell attract attention and bust the thief's eardrums. Of course you would probably have to hook it up to a ultrasonic system or a motion detector to only go off when someone is IN your car and not just walking by. Just a thought that I've been kicking around.

[ADA///M]

the pictures in this thread are hilarious

[petro]

and here is a pic of the mounting point on the console...

[trent]

Originally posted by ADA///M
the pictures in this thread are hilarious

I was just thinking that. I couldn't stop laughing. I am pretty confused! lol

[done] :yeah: