how can i fix my vokera combi boiler????

When operating the filler valve can you hear any water flowing into the system. If you cant then it could just be a faulty filler valve.
If you can hear water check if it is coming straight out of the pressure relief. A pipe comes from a valve under the boiler and will go out through the wall. This is there to let off pressure if it gets too high. Sometimes these will go faulty and contantly let pressure release from the system. If this is the case you will need to replace or call someone in to replace it.
If neither of these is the cure you may have a serious leak somewhere on the heating system pipework.

Robin S
September 2008