Set Appliance State:
Gas Off
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Ensure the boiler has reached its full operating temperature
Measurement:
Remove the violet wire from the thermistor and measure the resistance across the terminal on the thermistor and the boiler chassis.
The resistance measured will depend on boiler temperature and should lie between 200-300ohms with the boiler at its full operating temperature (approximately 80 degrees C).
Replace lead after test.
Note:
It may be necessary to reduce heating load by turning off some radiators to reduce time taken for this test.
The resistance measured will depend on boiler temperature and should lie between 200-300ohms with the boiler at its full operating temperature (approximately 80 degrees C).
Replace lead after test.
Note:
It may be necessary to reduce heating load by turning off some radiators to reduce time taken for this test.
Isolate as per TOPs P4
and refit as necessary