Marker Lights

[dirtyshoprags]

I just wanted to ask a quick question about the marker lights on my 65 C20. I'm replacing the existing marker light wiring and I have most of the bugs worked out except one. When I pull the headlight knob out one click the tail and marker lights come on. But when I turn the head lights on, the marker lights go off. Now, my question, is this supposed to happen? The lights didn't work when I got the truck so I don't know. I would assume they are supposed to stay on when the headlights come on, but I just don't know. I've tested the harness and checked the wiring on the headlight switch and everything seems to be in working order, but the marker lights go off when the headlights come on. Also, the blinkers still work when the headlights are on. Anyone have any input?