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1998 AU Fairmont BCM Questions 


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 Post subject: 1998 AU Fairmont BCM Questions
Posted: Fri Nov 12, 2004 5:03 pm 
Parts Gopher

Age: 31

Posts: 96

Joined: 8th Nov 2004

Ride: AU Tickford Fairmont

Location: Coolangatta
QLD, Australia

Hi guys,

I am going to get an alarm for my 1998 AU Fairmont, and alot of them have features such as interiour illumination, flashes indicators and crap that my fairmont already does when it is unlocked via the standard keypad. I guess that when you press the button on the keypad, the car recieves it and sends a signal to the bcm to do all these things. Is there a way that i can tap into this wire or signal so i can hook an alarm up to it so that it unlocks all doors, interior lights come on and indicators flash, or do i have to wire them up again separately through the alarm???

Also would anyone have a wiring diagram for the BCM (What wires go where and control what).

Cheers Guys
Posted: Fri Nov 12, 2004 6:36 pm 
Site Admin
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Age: 41

Posts: 514

Joined: 5th Nov 2004

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Ride: V8 VE Calais V Spec

Power: 262 rwkw

Location: Sydney
NSW, Australia

There isnt a nice way of doing this... Though it is possible !

Basically you need to trick the BCM/Bem in to thinking that certain things have happened, when your alarm system locks and unlocks the doors.

First Trick - Getting the Interior Lamp to Illuminate when your disarm your alarm.
You will need a couple of diodes here, you will see what I mean.
Feed the Negative Unlock Line from the alarm system, to the BEM Door Open Line.
What this does is tricks the BEM into thinking that a door has been opened, and closed, and it will turn on the interior light delay circuit, thus Illuminating the Lamp.
The problem here though is that this door open signal will feedback in to the alarm system, and the alarm system will think that the door has been opened, even though it hasnt.
This will cause problems if you alarm system has an Auto Re-Arm function. (The Function that re-arms the alarm, and locks the doors, if you have accidently pressed the disarm button).
The way to fix this is to place a Diode in line with the Door open line on the Bem. (Cathode to Door Switches, Anode to BEM)
Then wire the door open sensor line for the alarm between the Diode and the door Switches.
And finally, wire your Alarm Unlock Line between the Diode and the Bem.
You will also need to place a diode in line with your alarm Unlock line, right at the point where you splice in to the BEM, with the Cathode side going to the alarm, and the Anode to the Door open line on the Bem.
This will prevent the Doors from unlocking when a door is opened. (Although the front doors do this automatically with AUI models)

Step 2 - Turning off the Interior Lamp when you arm your alarm
This one is a little bit simpler than the above hack.
Basically you want to feed power to the BEMs accessory line, using a relay, that is triggered by the alarm lock line (Negative).
What this then does is tricks the BEM in to thinking that you have turned the ingition key momentarily in to the Accessories position, and will then switch off the lamp

I did write a doco on this one a looooong time ago, but didnt quite finnish it off.....
Ill see if I can dig it up, polish it off, and throw it up on the site, as it explains these steps a lot better than what I can in a 10 minute post.

Also, I believe that we have the AUII Bem wiring info in the docos section.....
If it isnt there yet, then please be patient, as I am stripping a lot of redundant HTML code out of my old Doco Backups, so as the load nice and quick, and dont chew bandwidth up....




VE Calais V8, IQ, HSV instruments and brembos fitted.
IQ, IPC, BCM all hacked and programmed without TECH2 :)

Posted: Mon Nov 15, 2004 1:41 pm 
Parts Gopher

Age: 31

Posts: 96

Joined: 8th Nov 2004

Ride: AU Tickford Fairmont

Location: Coolangatta
QLD, Australia

cheers, thanks for the help there. It will definately be helpful.
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