Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove left - hand side boiler case
Remove electrical connector to the gas valve
Remove electrical connector to the gas valve
Measurement:
Test 1:
Measure for resistance across the two outer gas valve terminals 1 & 4.
Expected resistance approximately 54.0 Ohms.
Test 2:
Measure the resistance between one of the outer gas valve terminals either 1 or 4 (it does not matter which) and a suitable earth.
Expect a resistance of 1MOhm or greater.
Are the resistances measured as expected?
Note.
Ensure a good connection is made as misdiagnosis will occur.
Measure for resistance across the two outer gas valve terminals 1 & 4.
Expected resistance approximately 54.0 Ohms.
Test 2:
Measure the resistance between one of the outer gas valve terminals either 1 or 4 (it does not matter which) and a suitable earth.
Expect a resistance of 1MOhm or greater.
Are the resistances measured as expected?
Note.
Ensure a good connection is made as misdiagnosis will occur.
Isolate as per TOPs P4
and refit as necessary