Glow-worm COMPACT 100p Instructions For Installation And Operation Manual page 30

With the boiler cold, check connections of the thermocouple, boiler overheat cut-off and gas valve.
Disconnect overheat cut-off connectors at points A and B at the gas valve, see diagram.
Test continuity of the overheat cut-off. Is there continuity?
YES
Re-connect boiler overheat cut-off to points A and B.
Disconnect thermocouple at point D of the gas valve.
Test continuity between point C and the body of the
gas valve. Is there continuity?
NO
Test continuity of thermocouple between inner
point D and point E. Is there continuity?
YES
Thermocouple and boiler overheat circuit satisfactory.
GAS
CONTROL
VALVE
THERMOCOUPLE FAULT FINDING
221680G
13 Fault Finding
BOILER
OVERHEAT
CUT-OFF
CONNECTION 'C'
Faulty boiler overheat cut-off,
renew.
YES
Faulty cut-off connectors into
gas valve. Either at A or C.
Renew where faulty.
NO
Faulty thermocouple, renew.
CONNECTION 'A'
CONNECTION 'D'
CONNECTION 'B'
30
NO
CONNECTION 'E'
Diagram 13.5