Relay/Isolator

Looking for just a little wiring help here. I have a power inverter in the back of my work truck to run my computer, printer and a few other items. After leaving it on and killing my battery a few too many times, I decided to install an isolator to work as an ignition on relay for it. I am using a Stinger SR80 isolator. I have it working fantastic to turn the inverter on with the key on, engine off. But when I start the vehicle, it loses the power signal and sets the no voltage alarm off on the inverter and kills it. This is a 2003 Chevy Express van (3500 series). I used the orange wire at the ignition harness. Can someone let me know if there is a wire that is ground at Key on/engine off, then goes to 12 volt at cranking and while running? Thanks in advance for the help.

There should be a pink heavy gauge wire in the ignition harness that is hot in run or start. Make sure to meter it, but that should be the right color.C Renner's Auto Electronix

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