engining running signal (wire)?

Can someone tell me where, in the engine compartment - not on the switch, to find a wire that is at +12v when the engine is running (not
cranking(, and at ground when engine is not running? '97 Sierra 1500 C/K I want to control a camper battey solenoid disconnect. Thanks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.