Vaillant ecoTEC Boiler Error F75 (F.75): Why Topping Up Pressure Doesn't Fix It & Solution
If your Vaillant ecoTEC Plus, ecoTEC Pro or turboTEC boiler displays Error F75 (or F.75), you may have noticed something puzzling: the gauge reads a healthy 1.5 bar, you press Reset, the boiler tries to start 5 times, and it locks back out on F.75. Here is why topping up water doesn't clear F75 and how we fix it.
What Does Error F.75 Mean on a Vaillant Boiler?
Before firing the burner, a Vaillant boiler briefly starts its circulation pump and checks whether the electronic pressure sensor detects a dynamic 'pressure jump' of at least 50 mbar (0.05 bar). If no pressure surge is detected after 5 attempts, the PCB locks out with Error F.75.
The 3 Real Causes of Error F.75
1. Blocked electronic pressure sensor (65% of cases): black magnetite sludge clogs the sensor diaphragm so it can no longer sense the rapid 0.05 bar pump surge.
2. Weak or seized circulation pump rotor.
3. Trapped air or flat expansion vessel absorbing the pump pressure impulse.
Our 24/7 Vaillant boiler specialists in Barcelona, Badalona, Sabadell and Girona carry genuine Vaillant pressure sensors and pumps in our mobile workshops to fix Error F.75 in a single visit. Call 936 94 00 23.
FAQ
What is the difference between Vaillant Error F22 and Error F75?
Error F22 means static water pressure is below 0.5 bar (boiler needs refilling). Error F75 occurs even at 1.5 bar because the sensor fails to detect the pressure jump when the pump starts.