BoilerFaultCodesWhat the manual says
Manufacturer manualSet diverter valve position
What causes this fault?
This code appears because the boiler has been manually instructed to hold its internal diverter valve in a specific position for testing purposes. This usually happens during a professional service when a technician needs to isolate the heating or hot water circuits to check for leaks or performance issues. If the code remains on the screen, the boiler has simply not been exited out of this specific diagnostic menu.
DIY fix possible
Locate the display panel on the front of the boilerPress the 'Reset' button (marked with a flame or cross symbol) for one secondWait for the boiler to restart and check if the 'D.70' code has disappeared
Avoid the next call-out bill
A cover plan would handle faults like D.70: no call-out fees, no surprise bills.
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Related fault codes
All 135 fault codes on the ecoTEC plus 612 R1 VU GB 126/3-5
Seeing a different code? Every code this model can display, in one place.