12v on negative wire normal?

Ok I have a dei proxitmity sensor that uses a ground when arm input, 12v power input, a warn output and trigger output. When the sensor is hooked up I get 12v on the negative warn and negative trigger output wires. Everything is working but is that normal? Same happens to my relay that powers my headlight, I used 85 trigger from the alarm (-) accessory wire 86 and 87 to 12v and 30 output to my (+)headlights. I'm getting a 12v signal from terminal 85. Again it works right but i'm just gettin a 12v signal, either when it activates or rest. Does this have anything to do with having a diode installed on the relay? I tried putting a diode between 85 and 86 with a 3amp diode the band towards positive, and same thing still happens.All of them recieved about 12volts but my test light is dim. Does it suppose to be like that and Why would a start/igntion kill circuit require a diode installed and other applications wouldn't need it? Hope you guys can clarify for me thanks

This is perfectly normal. Its kind of hard to explain why this happens, but you can think of it like this. In a car, for something  to happen electrically, both power and ground have to be present at the component that is supposed to be doing something. the components these wires  are attached to inside the sensor, have the power the need on one side (which is what your meter is picking up) all the time, therefore a ground is all that is needed to cause an action, in this case, triggering the alarm? make sense? Northstart.....or start it your damn self.

Ok cool as long its normal, but how about a diode on a starter/ignition kill relay, why is that needed and other applications not? thanks again

ttt

anyone?