Set Appliance State:

Mains Power Off
Set Multimeter to Resistance Set meter to measure resistance
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4

Measurement:

Disconnect the two wires from the water section rear microswitch and measure the resistance across the microswitch terminals.
Repeat the test with the water section front microswitch.
Reconnect wires after test.