Heater not working

[orthas]

OK I know this has been asked a million times and I have read them all. Heater is only blowing cold air. Have replaced heater tap, radiator, thermostat and intake manifold gasket. The heater tap isn't moving, I can move it manually when on hot but not on cold. I assume this is a vacuum issue. Is there an easy way to test them as they look quite hard to replace.

Thanks
Jeff

 

[Lex]

Have a look at the one way valve on the back of the plenum.
Look at the heater tap, notice the small vacuum line? Now follow it up to one valve behind the plenum. Take it of by just pulling & twisting it.
Now blow in it ( no blow?) then suck on it. If you can't blow or suck,its blocked. Needs replacing.
Very cheap from holden.
Here is a pic of what it looks like.
This is my old one. Recently replaced it.