Jan 152011

Testing a dishwashers components is done with a volt meter, having a volt meter to help with diagnostics is essential.

The heating circuit on a dishwasher contains several parts any of them could cause the dishwasher not to heat possibilities:

-Faulty heater element
-Open thermostat
-loose or broken wire
-Failed electronic control
-Door switch

Any of these components if broken will create a no heat condition.  There is a schematic and wiring diagram on the machine, if you can read a schematic you will see the circuits in the series.  If not on some technical schematics there is information on accessing the dishwasher diagnostics.

In diagnostic mode you can manually advance the unit activating all of the functions this will allow voltage tests if needed. This test lets you advance the unit through all available option without having to wait two hours for the cycle to complete.

Jan 152011

Bosch dishwashers are built with flood switches located in the bottom base pan of the dishwasher. The flood switch is connected to a rod that activates a small interlock switch, when water enters the base pan on a Bosch dishwasher a Styrofoam puck lifts the rod activating the flood switch.

When the flood switch is activated the dishwasher will go into a no fill,  only drain mode, the drain motor may also run with the door open to the unit, this is a sign there is water in the base pan.

Determining where the water entered the base pan can often times be time consuming. Bosch dishwashers have a more complex wash and dry system, more parts this mean smaller work areas, some parts are in sealed compartments, these require lots of time and effort to access.

You may have to watch the unit through a complete cycle before you can diagnose the error. Some of the more common possibilities include

-Sump fill hose (Cracked/brittle)
-Drain hose(Also check drain hose connection)
-Faulty drain pump seal
-Circ pump housing’
-Main sump seal

Any one of these are a possibility and there are many more, spending an hour watching the unit cycle may be the only way to figure out where the water is coming from.

Note also over sud-sing will also cause the unit to leak water into the drain pan. If you recently filled the dishwashers jet dry dispenser, excess jet dry on the door and surrounding areas could create the dishwasher to flood into the pan.