Did it have a timer? My donor was a 92 and had the switches as you describe. In 86 the door jambs are tapped much smaller and thus I didn't install the door switches right off. (Still haven't, actually) So my switches are unplugged and the lamp only comes on with the switch in the dash. I disabled the switch in the hatch because I frequently leave it open for hours.
As setup, it doesn't have the delay feature, but it did work fine in the donor. If your switches are unplugged and it's still on, I'd guess your problem isn't with the switch. High resistance to ground may have killed the timer module, I'd look there.