PRIMARY SENSOR (HIGH FLAME)

Isolate Mains Power to appliance as per TOPs P4

Set Multimeter to Resistance

Disconnect plug (red leads) from primary sensor
Ensure primary heat exchanger is below 40° C, carefully remove sensor

Measure resistance across the exposed sensor terminals.

Resistances vary with temperature and should conform approximately to the table below:

Note: Clicking on the resistance table will switch between table and graph view.