Logic / Voltage when alarm is set?

[omega1]

Hi all,

I'm looking for a logic or voltage that will indicate when the alarm is set? Does anyone know where I can find such a supply? Basically looking for a +12vdc that is only present when car is locked and alarmed, thanks.

 

[jaymanek]

im not sure how modern can based systems work but i know on the older cars you could get this from the central locking pump.

 

[Dec]

The internal motion detectors would need power to monitor the inside of the car when the alarm is armed, that is providing the are enabled i.e. the are on.

If there is a LED on the dash or inside of door that lights up to indicate to prospective thieves that the alarm is armed then that would also be a source of power however it may not be of any use to you if it is intermittently flashing on and off.

Dec

 

[omega1]

Hi, yes, I was thinking about getting the source from the LED to be honest, I'll have to adapt it to cope with the flashing though!

Thanks

 

[Dec]

I doubt that it can be adapted, the alarm circuit board will have something to make the LED blink, you will have to bypass that and that will involve some surgery to the PCB.
You really need to get this power supply from a wire coming from the alarm PCB rather than the PCB itself.

There is one other place for a power supply, that is, if it is fitted to your car, the anti-towing device located in the boot, I think, it is enabled or disabled by a switch on the dash.

Dec

 

[Dieselman]

Is the alarm a self contained unit on a W203, if so the feed into that should switch appropriately.

 

[omega1]

Hi all, thank for your input.

I'll be able to adapt the flashing LED as a suitable source, but would prefer a good ol' 12vdc source to avoid extra circuitry.

If the alarm 'is' a self contained unit on my model (I don't know) where is the unit located?

Thanks again.

 

[Dec]

Where it is location on your car, that I don’t know.
As I understand it an alarm always has power going into it, it is always on, it needs to keep back up batteries toped up for the siren and is always awaiting a signal from a key fob so as to arm/disarm so it is on stand by all of the time.

Yours could be a different set up as Dieslman suggests, without testing or wiring diagrams it’s difficult to say what’s live and when it’s live however the other sensors mentioned above would have power when the alarm is armed.

Dec