Is the heating element working properly?
Instruct the customer to run a cycle with the Sanitize option selected. This will cause the customer to have to call back after the cycle has completed but inform them that this will help to determine if there is a mechanical problem with the dishwasher. If the Sanitize LED is on steady (not blinking), there is no problem with the dishwasher's heating element. If the Sanitize cycle has completed, the dishwasher has reached its max temperature, therefore the heating element (which performs the drying function) is working properly. Inform the customer that today's dishwashers are more energy efficient and the key to optimal drying performance is proper loading and the use of Rinse Aid.
If the Sanitize LED is blinking (not on steady), there may be a problem with the dishwasher's heating element. If the customer has already run a cycle with the Sanitize option and has called back in schedule service.