when van is running headlight switch off, shut off engine headlights come on and stay on

Your headlights are controlled by the Body Control Module via Low and High beam relays. It is possible that you have a faulty headlamp switch that sends a false "ON" signal to the BCM although you turn it OFF. It could also be caused if the low or high relay is bad ( stuck closed). The relays are located in the underhood power distribution center, try to remove and swap it with the horn relay. If it is not the relay issue, then you will need to have it diagnosed with a DRB III scan tool in order to minitor the BCM input/output data. Try switching the relays first and then try a headlight switch.

I replaced the headlight switch,and the BCM. I will try relays again. I haven't checked them sence I changed switch and BCM. Thanks for your help