Either you have an air bubble just before the heater or your heater valve has failed.  The arm may be moving but not the ball under it.
Z

    On Thursday, October 11, 2018, 9:58:20 PM EDT, Don Hanson <dhanson928@GMAIL.COM> wrote:  
 
 How does a Vanagon heater fail?  Mine doesn't leak, the dash lever moves
the valve just fine and hot coolant gets to the check valve, at least, but
no heat.
  It worked fine, then I replaced the thermostat..No work then..So I undid
my "repair"... but the heater didn't come back.
    I've driven the van both ways, bled it with every trick I've devised
through 3 motors and half a million miles...no heat.  Anybody? Thanks