Peterbilt 365 easy jake

I’m wiring in the easy jake brake switch on my 09 Pete 365. It’s moved the switch on the dash to the shift column. Directions say there will be a constant hot going to the factory switch, found that. Then it says when you turn the switch on there will be another hot that shows up. Can’t seem to find it. The factory switch light comes on but there’s only still one constant hot that shows up. I’ve tried it with the truck running, in gear with the jake on and still the other hot doesn’t show up. Any ideas?