My Ravenheat combi boiler RSF820/20T 3 way diverter valve failed and I have just replaced it. While the domestic hot water flows freely through it the central heating portion refuses to fill. What is odd is that there is an arrow on one port of the valve which one would assume indicates direction of flow but the only way the valve fits has domestic hot water flowing out through that port when the arrow indicates in the other direction. I am absolutely positive the old valve was fitted in the same way. Any suggestions would be appriciated, it may be spring time but it's still wooly hat weather in Aberdeen.
Inspect your central heating system for a bleed valve, hook a hose to it (if found), open the valve, and turn the system on to heat. If it is an air lock in the system this should bleed it out. You may also have to remove a cap on the pump for the heat system, and force the pump to start up (usually done with a screw driver), then bleed the system out.