Home Heating System Vaillant 835/E2 - F25 ERROR?
Hi,
I have had the error F25 appear on my boiler and as a result have filled it with water to raise the pressure levels to between 1 and 2. However after 15-20 minutes the pressure level is back to zero and the error F25 is on screen again. I have checked that all the radiators are hot which they are and cannot see a visible leak. Please help!
Vix, April 2009