Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect red leads from sensor
Measurement:
Check resistance across sensor spade terminals.
Resistance measured should be less than 21kOhm.
Note:
Resistance measured will vary according to boiler temperature the colder the boiler the higher the resistance. If the boiler temperature is above 9 degrees C then frost protection should not be activated.
Resistance measured should be less than 21kOhm.
Note:
Resistance measured will vary according to boiler temperature the colder the boiler the higher the resistance. If the boiler temperature is above 9 degrees C then frost protection should not be activated.
Isolate as per TOPs P4
and refit as necessary