16 | P a g e
5. Check for Voltage at the pump:
• You can force the pump by removing the PWM cable to allow 230v cable to power pump at full
speed.
• If pump does not run via above test check, check 230v across PCB connectors X9, pin 1, and X10
pin 2. If no voltage present, replace PCB.
• If voltage present check pins on pump PWM connector are not bent – straighten to fix if
required, and check continuity of wiring harness.
• Check the pump PWM via the 2-wire cable connection to the pump on PCB connector X1 pin
1&2:
I. with the pump off the voltage is +/- 9VDC.
II. On pump startup the voltage is +/- 1VDC.
III. Pump overrun approx. 4.5VDC
IV. Normal running approx. 4.3VDC
6. If the voltages are incorrect, replace the PCB.
7. If the voltages are correct, replace the pump.
Blank display screen.
Cause: No power to boiler, internal fuses blown, display fault, PCB fault, fan or pump faults caused PCB to blow.
1. Check fuse at fused spur.
2. Check 230v into boiler.
3. Check continuity of fuses F1 & F2. Replace as required.
• These fuses protect both the live and neutral circuits only and are not specific to components or
internal circuits.
• Note the boiler is not polarity sensitive however polarity must be correct for safety.
4. Check fan resistances per 151 fault code. Replace fan as required.
• PCB will also need changed as fan has taken out board.
5. If fan ok, check pump for smell of burning. Replace pump and PCB.
6. If fan and pump are ok, replace PCB.
Boiler heating – no demand & One Control connected.
Cause: Boiler is still operating with last command from controller, controller now lost signal to boiler.
1. Perform a factory reset on the controller by removing the controller from the wall. Then use a pen or small
screwdriver and press the reset button on the rear of the controller.
2. If the reset does not work, replace the One Controller.
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