Vaillant Ecotec boiler F75 Due to blocked inbuilt filter and sensor

This boiler was having intermittent failure to F75. During the investigation it was found that not only the sensor, but also the inbuilt primary filter is blocked.

The boiler was flushed and the components cleaned. New sensor and a magnetic filter installed.

Vaillant Ecotec boiler F75 Fault – cause and cure ( 7 causes + 5 step cure = Fault 75 )
* F75 Meaning = No pressure rise was detected on turning the pump
(approximately 0.2 bar increment needed)

• (This document is written only for a competent and registered Gas Safe engineer to help fixing the F75 fault. This applies throughout all Ecotec combination and system boiler models such as plus , pro, VUW , combination{ 824, 830, 837}, system { 612, 615, 618, 624, 630, 637 } ) The Author will not be liable to any damages resulting in following this information.
• If you have F75 error on Vaillant EcoTEC boiler display , reset the boiler to clear the fault. ( press the button with the flame / rabbit / cross on it)
• If it continues to show the F75 Error after multiple attempts to ignite, it may be due to one or more causes as listed below. ( the most likely cause at number [1 ]and the most unlikely but possible cause at number [7] )

Cause Cure – if find defective - replace or Repair
[1] Too little water in the system or air in the heating system due to defective automatic air release valve • check - water pressure - release air - adjustable bypass - expansion vessel

[2] Blocked Pressure sensor
( blocked sensing orifice ) • check pressure sensor -check built in filter
• check the analogue and digital water pressure readings for any discrepancy - if so it is likely that the sensor is blocked
[3] Faulty pump • check power supply to the pump - it is spinning ?
• If pump has the power but not spinning
[4]Blocked component on the circulatory system • connector hose / inbuilt filter or heat exchanger of the boiler - drain down and check the components
[5] Faulty Pressure sensor
• If it was found that no blockage on sensor or other components - pump working - no voltage increment on X2 Black and Green from 1.6 volt to about 1.9 volts when the pump is on
[6] Faulty PCB • no power to the pump during the ignition sequence while pump supposed to be powered ( When Pump sign is displayed on the display on EcoTEC+ Models )
[7] Faulty wiring • connection - no continuity on cables between the connectors

To fix the problem, the actual cause need to be identified and eliminated.

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