my Vaillant thermocompact combi will not light. fault no f.28?
I switched off boiler to flush out a cold radiator. Refilled system till pressure was ok,bled the system ok,switched boiler back on and after a minute or so fault no 28 is displayed.
In the manual this indicates no gas, bit all other gas appliances ok.Have tried resetting as stated in manual to no avail
Tom Patterson, January 2007