I've been trying to search around to see if anyone else is have a similar issue but had no luck. I'm hoping you guys can help me. I just bought a 99 silverado z71 not that long ago and it would seem that some of my interior system won't work unless I have my headlight switch on. So far the unlock side of my door locks wont work and my interior lights don't work unless the switch is on. It has the security light on but the truck runs and drives with no problems but it appears that the ignition has been changed before. What do you guys think?