Set Appliance State:

Mains Power Off
CH Demand
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance.
Does the boiler reset?
Allow boiler to run and burner to ignite.
Does the fault code reoccur?
FAULT CODE DOES NOT REOCCUR
FAULT CODE REOCCURS SHORTLY AFTER IGNITION
BOILER WILL NOT RESET OR REOCCURS BEFORE IGNITION
Note:
If after boiler reset the fault code changes from L7 to a different fault code, then CLICK HERE.