by check valve do you mean the valve that controls the coolant getting into
the heater core?  the only thing I can think of it's full of air.  Drive
some time with the lever on hot and see if it purges itself?
Edward

On Thu, Oct 11, 2018 at 9:58 PM 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
>