The Poskim discuss whether the same dishwasher may be used for meat and milk vessels, in separate loads. Hacham Yishak in Yalkut Yosef (Moadim II, Haga'alat Kelim) permits using the dishwasher on the condition that the dishes were rinsed well of all solid pieces of meat or milk. If only small traces of the food remain, the detergent in the dishwasher renders any remaining food "Pagum" (foul), and thereby avoids any problems of taste absorbed in the walls or racks of the dishwasher. The precedent for this is found in Maran who permits adding ashes to a mixture to prevent a prohibition of meat and milk. Rav Moshe Feinstein (Russia New York, 1895-1986), in his Iggerot Moshe, also permits this use, although for different reasons.
Technically, a dishwasher can be converted for Pesah use by cleaning and inspecting the grates for any traces of Hames. It is best to also run the dishwasher on an empty cycle to clean it out.
SUMMARY
A dishwasher may be used for consecutive loads of milk and meat dishes if the dishes were rinsed well before and soap is used in the dishwasher.
