Glow-worm SwiftFlow 120 Servicing Instructions page 13

YES
(a)
After about 30 seconds from
"switch on" does fan go to low
speed?
YES
Isolate supply. Restore
supply with no demand.
Is there 24Vac between
grey wire on CN6 and Pin 2
on CN1 for about 30
seconds.
YES
Isolate supply.
Reconnect CN6,
restore power supply.
YES
NO
Does pump run for
about 30 seconds?
YES
NO
After about 30 seconds
does pump go off?
YES
NO
Open DHW tap at full
rate. Does burner
pressure go to 13.1mb?
YES
continued
(a)
Supplied By www.heating spares.co Tel. 0161 620 6677
3 F a u l t F i n d i n g
NO Isolate supply disconnect central heating thermistor,
is resistance of thermistor between 8KΩ and 11KΩ?
Faulty thermistor.
Replace.
NO Faulty APS.
Replace.
During the 30
second period is
there 240V at pump.
Faulty pump.
Replace.
Faulty main PCB.
Replace.
Is the burner
pressure between
0.1 and 13.1 mb ?
Does green
demand light
come on?
YES
continued
(b)
13
NO
Faulty main PCB.
Replace.
NO
Faulty main PCB.
Replace.
YES
YES
Check venturi air
signal at test point
Is this approx 2.5mb
NO
Faulty fan.
Replace.
Faulty gas/air ratio
NO
unit. Replace.
continued
(c)
YES
YES
NO
Diagram 3.8 cont.
221045A