24 | P a g e
4. Check the pump for air and vent the system if required.
• Use the boiler air purge to assist by turning off the power at the fused spur for 5 seconds and then
re-establish the power.
5. Check auto air vent is operating correctly and not contaminated with sludge.
6. Check the operation and voltage of the pump with a demand.
You can force the pump 'on' via 2 methods:
• Preferred and safest method by using the manual settings in parameter menu 2. Set parameter
2.6.0 to 1 = Manual mode On, and 2.6.1 to 1 pump control 'On'. Please note change 2.6.0 to 0
manual mode 'off' after this test.
or
• By removing PWM cable at the pump to allow the 230v cable to power the pump at full speed. To
do this, ensure safe electrical isolation and then use a 4mm electrical screwdriver to push down the
clip below the PWM connector and gently pull the connector out. Re-establish power to the boiler
and the pump should run at full speed.
7. Confirm 230v from the PCB connector CN2, pins 5&6. If no voltage, replace PCB.
8. Check 230v supplied from the PCB to the pump connector. If voltage at pump connector, replace pump.
9. If no voltage at pump connector, use a multimeter to check the wiring harness for continuity from the PCB
via connector CN2, pins 5&6, whilst checking connectors are tight and free from damage or corrosion.
Replace as required.
10. If 230v side ok, check the pump PWM via the 3-wire cable connection to the pump on PCB connector CN9
pin 1&2:
• with the pump off the voltage is +/- 5VDC.
• 39% load the voltage is +/- 3VDC.
• 61% load the voltage is +/- 1.9VDC.
• 100% load the voltage is +/- 0.24VDC.
11. If the above voltages are correct, and the pump does not operate, replace the pump.
12. If the voltages are incorrect, replace the PCB.
13. Check expansion vessel pressure is set correctly as per the manufacturer’s instructions.
14. Check expansion vessel flexi hose is correctly connected with no kinks or blockages.
15. Check the boiler for any blockages or restrictions.
16. After checking all the above points, switch off the power and back on again, allow the boiler to run
automatically through the automatic venting program.
17. If the fault persists, replace the PCB.
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