My BMW manufacture siren did stop working and as a result I bought an aftermarket siren which comes with a backup battery. The new siren has 4 wires, black(negative), red(Positive), Blue and White trigger negative and positive accordingly.
However my siren wiring is 5 which are brown and red for negative and positive and then other three which i am not sure how to exactly find which one of those is a trigger negative or positive.
What i did was I locked the doors using the fob and manually opened the door which triggers the alarm and then I looked for voltage on the 3 remaining wires :
here are the results:
red/brown wire: constant 0.54 v
black/white:around 0.2 to 1 V when alarm is triggered
purple: same as above
so I then used the black and white and connected the positive trigger and no alarm sound, i did that for the other 2 and nothing happened. I then used the negative trigger from the siren and connected it with the black/white which worked.
however here is what the problem is :
when i open the ignition key I can hear a small "ghzzzzzz" from the siren for less than a sec and then finish. so I went back and connected it to the negative trigger to the purple one and that fixed the ignition sound however here is what happens now:
when I looked or unlock the door I can hear a "ghzzzzz" sound and once inside the car the internal lighting make a funny "ghzzzz" noise when they turn on and off