Installation advise for Air dump switch for 388 Peterbilt

O your extra wires, is one yellow? According to this http://www.randpcarriages.com/tech/7waywirecolors.htmlm the center is yellow, of coarse this is a diagram for the green pig tail not the yellow so who knows.

 

im having no luck with this myself...I got a fl columbia and on our trailer its center on the yellow pig. The only hot wires on that are the abs wires. I cant find any wireing for the center pin which needs to be hot to activate the dump. It would be to easy if the manual had a wireing diagram

 

Im thinking of just ripping open the bundle of wires right behind the plug and cutting out the middle wire...then just running my own power strait to a fuse on the bat terminal....Ill add a relay switch and be done. Unless I can find out where it goes....but ill have to get off the computer and under the truck to try and find that.