Have you run DC voltage to your fan to make sure it isnt the fan? I havent made the jump to the Edge yet, but my Jeep Grand Cherokee had a similar issue and the fan relay was in a very unfortunate place (had to cut a small access hole in the plastic underneath the right headlight assembly since I did not want to pull the front bumper completely off) but after I replaced it finally it seemed to be OK for about a week and then the fan wouldn't come on anymore. Ended up needing a new fan, so it would have been beneficial to troubleshoot the fan first in my experience.
