Oh I see; it's not that it doesn't work at all - it's that it won't turn off when you slide the door shut? There seems to be a plastic moulding that fixes to the door. You can just make it out in this picture (click to see image full size)
unfortunately my van's not here for me to get a better picture

It's not a flat piece of plastic either. It's shaped like a boot and protrudes slightly if my memory isn't playing tricks on me. Is there another t25 nearby that you could have a quick look at?