Just had transmission replaced in my 2004 F150. Just went to turn the heat on and when I did interior lights went out, both blink lights on the dash came on, radio light went out and blinkers did not work nor did the heat. When I put the heat back in the off position everything else returns to normal. Any ideas???!

 

Did you check the battery terminals and connections? Also the starter connections, all of which should have been disconnected with transmission work.