Observation:

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RETURN TO CHOICE OF DIAGNOSTIC PROCEDURE
APPLIANCE DOES NOT ENTER STANDBY NO LIGHTS PRESENT
APPLIANCE DOES NOT REACT TO CH DEMAND
FAN DOES NOT RUN
FAN RUNS, SPARKING DOES NOT OCCUR
SPARKING OCCURS, BURNER DOES NOT IGNITE
BURNER IGNITES, BUT DOES NOT ESTABLISH (SPARKING CONTINUES)
BURNER IGNITES, SPARKING CEASES, BURNER GOES OUT
BOILER FIRES AND RUNS, CH OPERATION UNSATISFACTORY
CH OPERATION OK DOES NOT REACT TO DHW DEMAND