I have a combi Vaillant boiler. There is one key under the boiler. The pressure is low so i tried to turn the key to increase the pressure but it wouldn't budge. It will not move to the right or left and I cannot take it out either. How do I increase the pressure? Is there any other way to increase the pressure?

Some help please

jay sena, January 2012

Help what to do

Ann, February 2012

The pressure on myt boiler keeps falling- causing boiler to go off or not come on

ann, February 2012

It only hold by O ring ,spray with WD 40 wait 15 mi than right slow with plier ,no other way to pressure system,or fit filling loop

ltd, January 2012