my Vaillant thermocompact combi will not light. fault no f.28?

to fix this fault, underneath or around the boiler case somewhere, there is a little valve connected to pipe( in my boiler there is just one valve), open that valve carefully while keeping an eye on the Bar Gauge i said earlier. opening the valve MUST increase the pressure and push the gauge to the green area. when the guage hand reached somewhere betwwen 1 and 2, close the valve again and fire up the boiler... it should fix the problem....

Hadi
December 2010