Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect the orange lead from the condensate drain cap
(This should already be disconnected from a previous test)
Remove the 10 way connector from the ignition PCB

Measurement:

Test 1.
Measure the resistance between the disconnected orange
lead and pin 2 (orange wire) on the 10 way connector.
Expected resistance short circuit / zero resistance.
Test 2.
Measure the resistance between the disconnected orange
lead and a suitable earth point.
Expected resistance greater than 1 Mohm.
Also visually inspect the condition of the lead.