Just my curiousity but why does the ICE have to be on in order to put on the fromt defrost. I understand the Max A/C but not the Defrost. Anyone know why?

 

For many years now defrosters have turned on the A/C to remove moisture from the air to prevent the cold windshield from fogging up. Its standard, funny thing is when it wasn't done that way (when I was a kid) I don't remember the defrosters being much less effective, however it is what is done now.

So the reason the engine is locked on is because the compressor for the A/C is running while the defrosters are on.