Locate the detergent cup. The photo below shows a close up of a dual style detergent cup and the bimetal assembly. The dual style uses a bimetal switch for each cup. In the picture, the cup is open. If it were closed, the lever arm (partly out of frame) would swing down and lock into place in the bimetal assembly.
Before replacing the switch, check
the alignment of the assembly by latching the cup closed. With
a small screwdriver, gently push the metal until the detergent
cup opens. Some assemblies can be adjusted to improve the alignment.
If the alignment does not appear to be a problem, then remove
the assembly and replace the switch.
Label the wires and connections
so that you can properly reconnect them later. The wires are connected with slip
on connectors. Firmly pull the connectors off of the terminals (do not pull on
the wire itself). You may need to use a pair of needle-nose pliers to remove the
connectors. Inspect the connectors and the terminals for corrosion. If either
is corroded they should be cleaned or replaced.
Reconnect the wires to the new assembly and refasten the assembly to the detergent cup. Before replacing the interior panel, check the alignment of the assembly by latching the cup closed. With a small screwdriver, gently push the metal until the detergent cup opens. If it does not come open or does not latch, adjust the alignment so that the cup opens and closes properly. Replace the interior panel and plug in the dishwasher.