F3' - Fan Fault; F4 Or L4' - Flow Thermistor Fault; F5 Or L5' - Return Thermistor Fault - IDEAL LOGIC CODE COMBI ESP1 26 Installation And Servicing

4.7 'F3' - FAN FAULT

Does the wiring from the Fan to the PCB have
secure connections at both ends and has it not
deteriorated? Does the wiring have continuity?
Is there 230Vac at the Blue and Brown connections
to the 3 way connection on the Fan?

4.8 'F4 OR L4' - FLOW THERMISTOR FAULT

Is the wiring securely connected to the Flow Thermistor
(located in the top of the Heat Exchanger?)
Disconnect the wiring from the Flow Thermistor.
Check the resistance using a suitable multimeter connected
across the Thermistor's terminal pins.
At 25 C expect
o
At 60 C expect
o
At 85 C expect
o
Is the Thermistor value correct?
Is the wiring securely connected to the low voltage 6 way
connector at the front left hand side of the PCB?

4.9 'F5 OR L5' - RETURN THERMISTOR FAULT

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
o
At 60 C expect
o
At 85 C expect
o
Is the Thermistor value correct?
Is there continuity between the PCB and the Thermistor?
Replace PCB
Installation and Servicing
SECTION 4 - FAULT FINDING
YES
YES
9,700 - 10,300 Ohms
2,400 - 2,600 Ohms
1,000 - 1,100 Ohms
YES
9,700 - 10,300 Ohms
2,400 - 2,600 Ohms
1,000 - 1,100 Ohms
YES
YES
NO
Rectify Wiring &
connections
NO
Replace PCB
YES
Replace Fan
NO
Securely connect the wiring to the Water
Flow Thermistor
NO
Fit a new Thermistor
NO
Securely connect the wiring to the PCB
Replace PCB
YES
NO
Fit a new Thermistor
NO
Check and replace wiring as necessary
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