79
FAN FAULT
Rectify wiring & connections
no
Does the wiring from the Fan to the PCB have secure
connections at both ends and has not deteriorated?
Does the wiring have continuity?
yes
Replace main PCB
Replace Fan
no
yes
Is there 230Vac at the blue and brown
connections to the 3 way connection on the Fan?
80
FLOW THERMISTOR FAULT
Fit a new thermistor
no
Disconnect the electrical connection to the Flow
Thermistor and check the resistance using a suitable
multimeter connected across the thermistor’s terminal
pins.
At 25°C expect 9,700 - 10,300 Ω
At 60°C expect 2,400 - 2,600 Ω
At 85°C expect 1,000 - 1,100 Ω
Is the thermistor value correct?
yes
Check and replace wiring as necessary
Replace main PCB
no
yes
Is there continuity between the PCB and the
Thermistor?
81
RETURN THERMISTOR FAULT
Fit a new thermistor
no
Remove the Return Thermistor from the CH return pipe
and disconnect the wires. Check the resistance using
a suitable multimeter connected across the thermistor’s
terminal pins.
At 25°C expect 9,700 - 10,300 Ω
At 60°C expect 2,400 - 2,600 Ω
At 85°C expect 1,000 - 1,100 Ω
Is the thermistor value correct?
yes
Check and replace wiring as necessary
no
Is there continuity between the PCB and the Thermistor?
yes
Replace main PCB
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