ground when armed wire

I am trying to add a scanning led light to my Python 460HP alarm and use it in conjuction with the red status indicator light.  The led scanner will be used for greater "armed" visibility and not for alarm status.

My led scanner has three wires... red for constant pos., black for neg, and yellow for pos ignition power source if the light were to be used as a 'fake alarm'.  I tried connecting the red to a constant pos, and the black to the neg when armed wire (orange) and the led came on right away, and stays on whether the alarm is armed or not.

Am I misinterpreting that the neg when armed wire should only be neg (or a ground) when the system is armed?  It appears to be neg all the time.  Is this normal?  I thought installing this led would be simple, but maybe it isn't the case. 

Any help is appreciated.  Thanks.

Whenever more then one accessory is connected to the (-) when armed wire it's a good idea to diode isolate them to make sure nothing is backfeeding - especially if there is a starter kill relay involved.

The (+) side of the starter kill relays typically hooks to an ignition source.  When the ignition is off most cars ignition system rests at ground, allowing a weak ground signal to flow through the coil of the relay and possibly activate low current devices (such as LEDs or window modules).