2004 Silverado 1500 4WD Crew cab 5.3L
Your right of course, I was originally thinking that wire was being controlled by the control unit fan circuit but there's no red wire coming from the control unit. All the fuses are good. If you happen to know what fuse feeds that particular wire, I'll check the plug the fuse plugs into. Thanks for guiding me back to the path. I was getting into the weeds.Fix, your over thinking this problem.
It worked until it got wet.
The 12 pin plug to a 24 pin connector worked before it got wet.
If it looks fine, put back together before you have numerous problems and you won't get it fixed.
The red wire that has no voltage is supposed to be a fused 12 volt always hot wire, that's where your problem is, figure out why the 12 volts has disappeared.