i have a 2013 chevy 1 ton dually, doesel of course. after plugging in my block heater over night, it seemed hard to start. up untill now everything seemen fine. i do have 120 volts at my plug in.
So what's the deal mac? Is it working? Are your glow plugs working? Your block heater isn't what's making the truck hard to start in mild temperatures.
But then again, you haven't actually described the symptoms and are stuck on the block heater being bad, when that won't cause a hard start under your conditions. And a failed block heater is rare, unlike failed glow plugs.
Going to post more info or keep not addressing what you don't want to hear?