Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN302 from the PCB

Measurement:

Test 1. Measure for resistance across pins 2 (blue) and 4 (brown) of connector CN302.
Expected resistance, see table below:
ModelResistance (approx)
24 KW45 Ohms
28/32 KW22 Ohms

Test 2. Measure for resistance across pin 4 (brown) and a suitable earth connection.
Expected resistance greater than 1Mohm.