Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove 4 way gas valve connector from PCB
Measurement:
Test 1:
Measure the resistance across the red and black wires.
Resistance should be approx. 4.2Kohm.
Test 2:
Measure the resistance between the black wire and earth.
Expect a resistance greater than 1 MOhm.
Measure the resistance across the red and black wires.
Resistance should be approx. 4.2Kohm.
Test 2:
Measure the resistance between the black wire and earth.
Expect a resistance greater than 1 MOhm.
Isolate as per TOPs P4
and refit as necessary