Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Ensure boiler is cool
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does the appliance run and ignite for a CH demand or does the fault code reoccur?
Note:
If a different fault code appears click HERE to return to fault code page.