Dome light not working

[Maxian]

Bought a new dome light assembly and plugged it in.
Dome light is constant on. Only shuts off if I turn headlights on.
When plugged in and headlights are off, dome light is on with NO change when I turn switch to left. It will dim the dome light when turning to right.
New light came with wiring, one orange, one white wire with a T shaped connector.
I am plugging it into what I assume is the factory connector.
Same T shape, although it has a single white wire in one terminal and both an orange and yellow wire in the other terminal. This connector is right next to fuse box.
Truck is a 69 with no door pin switches so I "assume" dome light only activates when turning headlight switch to left ??
Thanks for any information. You have been a great help.

Brad