Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the leads from the gas valve
Measurement:
Test 1:
Measure the resistance across the two outer pins of the gas valve.
Expected resistance should be approximately 52 ohms.
Test 2:
Measure the resistance across terminal 1 (gas valve) and a suitable earth connection.
Expected resistance should be greater than 1 Mohm.
Note:
For clarity, gas valve has been removed from boiler.
Measure the resistance across the two outer pins of the gas valve.
Expected resistance should be approximately 52 ohms.
Test 2:
Measure the resistance across terminal 1 (gas valve) and a suitable earth connection.
Expected resistance should be greater than 1 Mohm.
Note:
For clarity, gas valve has been removed from boiler.
Isolate as per TOPs P4
and refit as necessary