Make sure dishwasher is filling up all the way. Most of them fill to the bottom of the lowest sprayarm. If you start it by turning a timer be careful not to turn it to far. It has a timed fill, if you turn it to far you are missing part of the fill cycle. You may have a long water line to dishwasher and it maybe filling with cold water on first fill. If it's hooked to the sink hotwater feed you might want to run hot water to sink before you start dishwasher. Just a few things that it could be. There is a screen in fill line at valve.