Vacuum - HVAC heater - Question

[83K20]

I have an 85 K20 - 350 - th400 truck.   I bought it used and as usual with buying a used truck everything was fubar'd

I'm trying to get the heater system to work.  blower works fine.

I Know I can hook hose to vacuum at the intake manifold runner but after that is where I need help.   Check valves, vacuum ball, how many vacuum lines go inside the cab to the control head?   Is there a heater control valve inline of the heater hose?  If so, where does the vacuum come from for that?

Thanks! 

[LTZ C20]

Look in the tech section of the forum, look at the service manual for your year and model, there should be diagrams and pictures of the whole system, where the vacuum lines go and to what they go too. Along with a trouble shoot for curtain problems and what to check for those problems.