Bosch dishwasher flow switch failure

Although Bosch dishwashers are highly rated by Consumer Reports, like all domestic appliances, Bosch electric components are subject to unexpected failure. The Bosch flow, or "float" switch, controls water flow much like the ball cock in a toilet cistern. However, instead of the float operating a mechanical valve, it engages an electrical switch that opens or closes the water intake valve. Consequently, a defective float switch will either stop water flowing into the appliance, or flood the dishwasher compartment and the kitchen floor.


The first step is to trip the dishwasher electrical supply switch on the electrical panel, followed by turning off the dishwasher water supply valve under the sink. Next, remove the two screws securing lower front access panel and undo the water supply line with an adjustable spanner. Remove the electrical junction box cover and note the orientation of the three wires before loosening the terminal screws and disconnecting the wires. Undo the screw holding the bracket to the terminal box and undo the conduit nut with a pair of channel pliers. Disconnect the water outlet pipe from the drain or garbage disposer under the sink and feed the pipe through the hole in the cabinet. Open the dishwasher door and remove the mounting screws from under the countertop. Loosen the dishwasher levelling leg locking screws and lower the dishwasher by screwing the levelling legs upwards with the adjustable spanner. Carefully slide the dishwasher out from between the cabinets.

Pressure chamber

Go to the back of the machine. Locate the white inlet water manifold on the lower left, and lift the inlet pipe out of the blue plastic pressure chamber. Lift the pressure chamber out of its base. Disconnect the water inlet hose by pulling it straight out of the bottom right of the pressure chamber, and remove the red float activator rod from the front of the pressure chamber. Unhook the float switch wires from the retaining clip and disconnect the wiring harness by pulling the plug out of the float switch with a pair of needle nose pliers. Pry the white chamber cover off the top of the pressure chamber with a flat head screwdriver; this will reveal the red plastic float.

Float switch

Insert the screwdriver tip into the recess on the float side of the switch and press it downward to release the switch retaining tab. Pivot the defective float switch upwards, slip the tab on the back out of its recess and remove the switch. Install the new float switch and push the front edge down until it locks into place. Position the chamber cover back onto the pressure chamber and press down until it snaps into place. Reconnect the wire harness to the float switch by pushing the plug all the way in, and then secure the wires in the retaining clip.


Reconnect the inlet hose. Lower the pressure chamber into its base while feeding the float activator rod through the mounting holes and into the hole under the float. Test the activator rod by lifting it up and down. Insert the hose manifold into the top of the pressure chamber to complete the reassembly.


Feed the dishwasher outlet hose back through the hole between the dishwasher cavity and the sink cabinet, then gently slide the dishwasher back into its recess. Reconnect the water and electrical supply lines by reversing the steps described earlier. Adjust the dishwasher levelling legs by rotating them downward with the adjustable spanner until the upper edge of the machine is level with the counter top; remember to tighten the levelling leg locking screws. Reattach the mounting brackets to the underside of the counter top and replace the access panel on the bottom front of the machine. Pull the drain hose through and reconnect it to the sink drain pipe or garbage disposer, whichever is applicable. Open the water supply valve, turn the electricity back on and test the dishwasher to ensure that it works properly and doesn’t leak.

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About the Author

After graduating from the University of the Witwatersrand and qualifying as an aircraft engineer, Ian Kelly joined a Kitchen remodeling company and qualified as a Certified Kitchen Designer (CKD). Kelly then established an organization specializing in home improvement, including repair and maintenance of household appliances, garden equipment and lawn mowers.