Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Remove plastic cover from the ignition control PCB
attached to the gas valve
Remove bottom molex connector from the ignition PCB (connector has 3 leads brown, blue and green/yellow)
Fuse F3 should now be visible

Measurement:

Remove fuse and check resistance.
Note:
Newer versions of the ignition PCB may not have the fuse fitted, if this is the case select that option below.