, the customer noticed the last time she started the dishwasher, everything seemed fine until the end when the pump was operating, but there very little water in the tub. After cancelling the wash and restarting with the same no fill results, she thought it was time to call for service.
Filling with Water
Dishwashers use a water valve controlled by the electronics or the timer to fill the tub with water. Most dishwashers (like this one) fill by time alone, meaning the valve is turned on for a set length of time in order to fill to the desired level. Because there is no way for the controls to determine how much water enters the tub, most of these dishwashers will use a float switch as a safety to prevent an accidental flooding condition due to to much water entering the tub. Depending on the make or model, these float switches may be located in various positions inside the tub, or in some cases in the sump or fill assemblies themselves.
Looking at the strip circuit for this Kitchenaid dishwasher, we can see the switch and valve are wired in series with one another (like the old Christmas lights), so if the float switch gets stuck in the open or flooded position, power to the fill valve will become interrupted and no water will enter the dishwasher. A great way to prevent your kitchen from getting all wet, but not so great if the switch gets stuck on accident.
What can go Wrong?
As I mentioned in the opening, this dishwasher stopped working at the end of a cycle after the dishes were already washed. The customer was using detergent tablets, the ones that look like little bricks with a ball in the middle. After the detergent dissolved during the wash, the ball was still intact and became wedged between the float and the tub preventing the switch from closing and allowing the tub to fill for the rinse cycle. Just a bit of bad luck for this customer, but it can be prevented. If you are someone that uses the detergent tablets, be sure and follow all the manufactures recommendations including those related to water temperature. If the temperature of the wash water is to cold, the tablets will not dissolve correctly and you may find part of the brick left over at the end of the cycle.