I have a kill switch located on my car and last night a 2 dollar toggle saved me a whole lot of cash. My car was broken into but all they got were tools and my radio. So I decided to beef up my security cheaply. I have a kill switch that is in series with the transmission switch and it seems to work great, the perps never got it started. Now I want to put in a switch that will kill the start solenoid. So I'm breaking the starter solenoid wire with a relay and the coil is getting power from my rear window defroster. My electrical is a little rusty so I want to know, should I put the relay coil in series with the defroster or wire off the defroster and go from the relay to a ground? In series the voltage will decrease with every load, so the coil for the relay will drop the voltage for the defroster. If I tap off the power and run it to ground in parallel I'm not sure if it will affect the amperage to the defroster. Any suggestions? Any other devices you would use instead of the defrosters? I don't have a hatch release button FYI.