BMW factory fitted alarm siren

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=32769
Printed Date: June 09, 2024 at 4:29 AM

Topic: BMW factory fitted alarm siren

Posted By: big_stoo
Subject: BMW factory fitted alarm siren
Date Posted: May 26, 2004 at 10:55 AM

Hi there!

Im trying to change the alarm siren on my '96 BMW 323 coupe to something with more volume. My friend has given me his old siren from an aftermarket Honda system. Its a no-name battery backup siren but has a great sound...

Anyway, my BMW siren and harness has 4 wires - 2 red, 1 black and 1 black with heatshrink over it. The no-name siren has 4 wires - 1 red, 1 black, 1 purple, 1 blue. Purple and blue are the +/- trigger wires according to the back of the siren unit. it also has a black 'soft chirp' wire which has to be cut to be disabled if required.

So, any ideas on how to wire this up to the existing 4 wire harness under the bonnet? Has anyone done this before, or should I give up now before I break something?

Replies:

Posted By: big_stoo
Date Posted: May 29, 2004 at 8:30 AM

bump

posted_image

Anyone got any experience with these cars? Its a factory fitted system as far as I know.

I just really need to know which wire goes where on the siren eg which of the two red wires is my power and which black wire is my ground etc, etc.

Posted By: draasch
Date Posted: May 30, 2004 at 8:49 PM

have you tried to use a meter on the wires??????

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Good Luck
David
Ace Security
813-376-9778
Tampa
Donate to the 12volt

Posted By: big_stoo
Date Posted: May 31, 2004 at 2:50 AM

I can borrow a meter to try, but i'm not sure what voltages to look for etc. I tried searching through the forum but Im still unsure, although Im OK with basic electrics. Thanks.

Posted By: big_stoo
Date Posted: May 31, 2004 at 2:53 AM

What puzzles me is the fact that there are 4 wires to the existing siren. I thought that usually a battery backed siren only has 3 (power, ground and 1 trigger).

Posted By: jimmeezgolfvr6
Date Posted: May 31, 2004 at 3:25 AM

actually, most backup battery sirens have 4.....you can choose to trigger it with either a positive or negative trigger. just a convenience feature. some older clifford backup sirens have 4 wires also, with the intention of connecting the 4th wire to ignition so that it charges up only when the ignition is on.

ultimately, on your factory siren, the wire you really need to find is the trigger. constant +12v and ground you can always get from elsewhere. of course, it would be so much more convenient if you can find those amongst those 4 wires also.

good luck!