Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Disconnect electrical connector from the fan
assembly, position in a safe place
Ensure No Demands
Preheat switched OFF (ECO button illuminated)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Click here for more information before carrying out this test.
Ensure appliance is not in lockout, reset appliance as required and no demands are present, pump not running (if pump is running restart test at SET APPLIANCE STATE).
Test 1: Measure for AC Voltage across terminals 2 (Brown) and 4 (Yellow) of connector ST5 with it still attached to the PCB and note the reading.
Test 2: Turn On DHW Tap
Measure for AC Voltage at the test points as in Test 1 again.
Expect an increase in voltage of approximately 1.0 VAC or greater from the original voltage measured on the first test. It can take up to approximately 20 seconds for the voltage increase to occur after a DHW demand.
Note: If the appliance locks out the voltage increase will not be present, reset appliance as necessary until test is complete.