Defrost on, truck dies...

[tex_waco_usmc]

Ok, so the other morning I went out and it was chilly so I turned the defrost on to warm the cab up a little. Drove to the closest gas station pulled up and the truck died and wouldnt start back up... Towed it home and threw it into park real hard and the truck started up again. I know I have a short in the column causing the no start situation (looking for a new column now with OD so I can match the 700R4 trans in it).

Few days go by hadnt really thought anything of it, until it started raining a cold hard rain and the windows started fogging real bad. Turned on the defrost and the truck died at a stop light! Fired right back up and died again until I reached over and turned the defrost off...

No idea what in the defrost system could cause the truck to not want to run... Any ideas???