car siren connection BMW 328i

[linux44]

Hi all,
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


any ideas?

 

[mattmoo1974]

Think you d be better of posting on the beemer forums mate....

 

[telectrix]

serves u right for having a BMW. (only jealous coz they don't make vans)

 

[linux44]

I did and not many people knew . so basically to rephrase my question I want to know how can i find the right positive, negative from a wire? I guess this will help me to work out which wire is for where.

and then try to find the positive/negative trigger which only has a volt in it when the alarm is activated.

I found the positive by using a multimeter and connect the black lead to the body earth and then do a volt test. there are 5 wires in total one of which has 12 V so I thought it is a constant positive.

the other 4, 1 of them has a volatge of 0.54.

i then used a continuity check to find the ground from those three" does continuity check damage a ecu or something? my understanding is that it send a signale so what happen if i by mistake connect a positive and negative lead and then do a continuity check ?

finally I was left with 3 wires which are the two wire that had no volt and the one which had 0.54v. i then activated the alarm and opened the door thus setting of the alarm and the result was that I had a voltage of 0.3 to 1 in the other 2 wire so here I am really confused on which on those three are the trigger positive or negative wire.

I hope this makes more sense and some one can help me .
@telectrix , you can try buying a sprinter or get a three series and add a wagon to it lol :d

 

[telectrix]

@telectrix , you can try buying a sprinter or get a three series and add a wagon to it lol :d

wouldn't have a sprinter as a gift. bloody rot boxes. suppose i could get a BM estate, cut the back off and fit a truckman top.

 

[linux44]

anyone please?