Who knows about proportional valves?

Ok I think o got things moving at least, so my son has a 80 s/b dodge so same frame/brakes I got him to send me photos of the valve to compare and it was the same, then I bled the front brakes first and stomped on the pedal several times, oh also my new one man brake bleeder showed up from Amazon today to so I used that and it had way more suction, I was then able to get fluid at all four corners, my pedal feels semi firm but there is still air in the system so I figure I'll just get one of my sons over to apply firm pressure to the pedal to force out the rest of the air but for now I tried one more trick, I have opened the r/r bleeder and left a hose on it in a pan to see if it will gravity bleed I'll check it before I go to bed and see if it's moving, if not I'll just bleed it with one of the boys then hopefully done. We'll I'm on the subject though any one have an idea what to hook the wire on the proportional valve to? There is a red light on the dash of this old truck I could use I am assuming it works like a oil pressure unit so it grounds?