Safari DRL (Day running light)

Good day all, you may have seem my previous post about my new GMC Safari 2000 Cargo van that I purchased. Another thing I have noticed once the car is running, the headlights+ parking lights SWITCH have no
effect on the lights at all.
Once the van is running, all lights are ON (headlights+parking lights). Does not matter if it's night or day there are always on.
There is a dome light overide button, the light switch and a dimmer button, is there anywhere that I could bypass the automatic mode of the lights?
What could cause this?
Thanks again, Ben

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