Where abouts? In the rear, there's a wire in the trailer harness for that, I believe its blue... quick voltmeter check can confirm.

 

Pink, ignition switch harness. Or https://sites.google.com/site/astrosafa ... /aux-power if it works for you. If you don't have the GM Techline eSI yet, you should definitely grab it.

Always use protection! Fuse/circuit breaker/etc.

I was planning on switching mine to an oil pressure switch, that way it's only connected when the alternator is running. It's an option

 

I was planning on switching mine to an oil pressure switch, that way it's only connected when the alternator is running. It's an option

Real quick I tried this and the switch only outputs about 5 volts. Not enough to trigger a relay. If you got it to work I may need to take a closer look at mine, but for now I could not find an "only hot when running" 12v+

 

That's a neat idea. Maybe you could install a voltage regulator that'll step up the 5v to 12v to trigger the relay? I'm not sure how those sorts of things work, but I'd imagine they must exist since the 12V is getting "stepped-down" to 5V at some point in the harness.

I'll leave it to my more electrically inclined colleagues to answer this -- but it is an idea to get the proper voltage to trigger the relay.

 

I was planning on switching mine to an oil pressure switch, that way it's only connected when the alternator is running. It's an option

Real quick I tried this and the switch only outputs about 5 volts. Not enough to trigger a relay. If you got it to work I may need to take a closer look at mine, but for now I could not find an "only hot when running" 12v+

I should have been clearer on this, I'm going to install an additional oil pressure switch, and use that to trigger the relay. You could also use the fuel pump supply, it would turn on to prime, but then only stay on when the engine is cranking/running.