Vaillant ecoTEC plus F.75: pressure rise not detected

What Does Error F.75 Mean?

On the documented Vaillant ecoTEC plus, F.75 means the control did not detect sufficient heating-water pressure change when the pump started. The service list includes low fill pressure, air or insufficient water, expansion-vessel influence, pump or pressure-sensor faults, and their wiring; neither component is proven by the code. Applies to: Current ecoTEC plus boilers covered by manual 0020308121-04 This meaning follows current ecoTEC plus installation and maintenance instructions 0020308121-04. Older ecoTEC generations, commercial boilers, aroTHERM heat pumps, and regional variants require their own document. Owner-safe checks: Photograph F.75 and the visible pressure, note recent bleeding or filling, and inspect only accessible external pipework for water. Qualified technician: Pump, pressure-sensor, expansion-vessel, filling, venting, internal leak, wiring, gas, and sealed-case work requires a qualified heating engineer.