Do as D.Johnson says, but you will need to pull the dishwasher right out and ideally have someone help you tip it backwards slightly as this makes access to the lower tray easier, the Float switch is made from polystyreen so you do have to make sure you get in there to soak all water up, as only a little will keep switch activated. Plenty of towels recommended and abit messy, but well worth the saving on a call out fee.
Lisa Evans
January 2009