Door open warning light
 

I have a Mitsubishi Space Star, quite elderly but really nice to drive. I've only had the car a couple of weeks. I need to leave the tailgate open all day sometimes but I've noticed that even without the key in the ignition the door open warning light comes on and stays on. Is this ok? Will it run the battery down if it's on all day or doesn't it take enough charge to do that?

That is indeed strange. I don't know the answer and am disappointed that you haven't had a response with a solution. Maybe you can try to close the latch with your finger while the hatch is open thus having the warning light think it's closed. Just remember to unlatch it before trying to close the hatch to prevent damage.

The answer was quite easy really. Just close the latch over anything metal and ring shaped and the light goes out. You can actually buy a Ventlock that will keep the tailgate open but locked if you need to leave the car.
Apparently this happens with lots of different cars.