It does sound failed. For interest sake, did you take a Temp-gun reading of UTH while it was in the tank hitting the "desired" temperature in 45seconds? I would have Temp-gunned the area to see if it kept going past that mark and if it was indeed hitting that mark quickly. I have a very low differential on my UTH (90-92F) so it is basically always kicking on and off and almost never takes more than a few seconds to return to the kickoff temperature. When I Temp-gun the area it is always at the desired temperature.