south georgia mechanic

I have a 2004 f150, when i try shifting into 4/4 with selector switch it will go into 4h and back out with selector switch, but when i shift to 4l it will not enguage nor will the light illumanate. I can pull relay ro-1 and jump between pins 30 and 87 and it will shift into low range but will not shift out with selector switch. I can pull relay ro-2 and jump pins 30 and 87 on that relay and it returns to 2h. If anyone can shed some light on this problem it sure would be greatly appreciated. I have checked fuses and vacuum relay and all this is operating as it should.