Defrost buttons new function: turn the car off after key is removed

[Vkoslak]

I haven't had time to recheck my wiring yet. But right now, sometimes when I put the key in the off position and pull it out, the car keeps running. I noticed the led for rear defrost was on. I pushed the defrost button and the car shuts off.

If it isnt something obvious, like I spliced something into the defrost wire, what should I start checking?

If a ground is missing, could it be electricity just finding the shortest route?

Car runs fine other wise. (well, it backfires between shifts, but I think that is an exhaust leak.)