Alarm Wiring Backwards?

Question

This vehicle is an Isuzu NPR Eco Max box truck cab.   I am finding that the door trigger wire is at 12VDC when closed!   Then as the door opens, the wire drops to 0VDC.    What do I do with this when wiring the alarm?   What input do I use?

 

The parking lights are doing the same thing.   12VDC when off and drops to 0VDC when you turn them on?!?  Im confused and not sure what polarity to set the alarm to operate the parking lights?

 

Any help would be much appreciated!!

Answer 1

Normally this means that your parking lights operate from a negative trigger.

I have never seen this vehicle so test your wires carefully. This one is at your own risk.