Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Gain access to PCB (use insulation mat as required)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Set multimeter to frequency mode by setting multimeter to AC volts and then pressing the yellow button.
Measure the frequency between pin 9 (Blue) and pin 8 (Black) at connector X8 on the PCB.
Please select option from below:
FREQUENCY BELOW 30Hz
Insufficient flow rate
FREQUENCY BETWEEN 30-50Hz
Lower flow rate
FREQUENCY OVER 50Hz
Normal flow rate