Basically, it should be getting power whenever the dishwasher should be filling. If it WAS getting proper but NOT filling the machine, the valve would likely be defective and need to be replaced. They can sometimes be intermittent, working once or twice but failing other times.
** it used to get stuck in the rinse cycle, supposedly heating the water. It would get unstuck by itself and finish the cycle well, about 20 minutes later than expected. **
"Thermal delays" can occur if too cool of water enters the dishwasher. Manufactures recommend a water temperature between 120-140°F. If colder, the dishwasher will stall to try to heat the water itself if on a wash setting which is designed to heat it.
Running a tap at the sink until running hot *before* starting the dishwasher assures the hottest possible water is entering the machine, not just luke warm to start. If you keep your water heater set low, you'll just have to put up with delays if you choose a wash setting which heats the water.