Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove fan/manifold assembly
Remove the burner/baffles assembly

Observation:

Inspect burner/baffles for debris, damage and
good general condition and are fitted correctly.
NOTE:
This component requires the air/gas manifold
and fan assembly to be removed therefore
the gasket between the gas air manifold
and the heat exchanger must be changed.