Anyone fitted OBC with factory alarm control unit?

[jimf]

Hi folks,

I am in the process of retro fitting an OBC. I haven't bought the relay yet but when I dropped the ECU down I discovered the blue factory alarm control box.

I assume I still need the relay (do I?) but the alarm box has the same two corresponding green sockets for the plugs. the car is loomed with the horn and a green plug for the alarm box. It was unplugged, probably for a reason.

How do I plug in the relay and alarm box together?

Also if this is how it works I will end up with two green plugs under the glovebox, one will be redundant so this makes no sense.

Finaly, what has the alarm horn got to do with the OBC?

[daimlerman]

The OBC based imobiliser/alarm is about as crude as crude gets!

The two greens,one each plug into the greens behind the glovebox...the alarm horn works in conjunction with a code that you enter into the OBC,the theory is that the horn sounds when you attempt to start the car without first entering the correct code....bypassed by un-plugging the above green wires and re-connecting the original loom.
This is a 'feature' of the OBC that is best left dis-connected with the horn placed in the bin.

[jimf]

Well i definately can't be bothered entering a code every time. I aready have to press a button on the fob to disable the immobiliser and that's too much effort as it is!

So do I ignore the alarm box and just fit the two plugs to the relay? or does the alarm box take the place of the relay?

[daimlerman]

As I guess you know,the solid green is the ign switch to coil feed,so interupting it means that the car does not start.The box that fits above the engine ECU interupts the green,but deleting it only removes the 'alarm' function on the OBC.

So by not fitting the thing and it's relation the horn,the OBC will still give you date/time/range etc,as well as looking on the dashboard!

[jimf]

Sorry I'm not quite with you. Are you saying I can delete the blue alarm box?

What does the relay actually do?

[daimlerman]

Sorry I'm not quite with you. Are you saying I can delete the blue alarm box?

What does the relay actually do?

I'm not sure what your 'blue' box is...there's a box that mounts above the engine ECU that is part of the OBC,this bit and it's horn can be deleted.This box has little inside it and just appears to control the immobiliser mentioned above.If your mystery box is wired into the car,proceed with care,tracing each wire from it so that circuits that it iterrupts can be restored.

[jimf]

I did plug the two greens into the alarm box just to see what happened and the car started just fine. Don't know if any of the functions would work though, depends on what that relay does.

[jimf]

It's not a mystery box, it's the factory alarm control box with bmw part number on it. It's mounted above the ECU where I was expecting to mount the relay

[daimlerman]

The OBC mostly gets it information via the instrument cluster,the green plug on it's harness.

[jimf]

OK, I'll just plug it all in and see how it goes when I take it for a drive. Perhaps If you have the factory alarm you dont need the OBC relay