Lionel,

I guess you have no aircooled. On this vans this failure is very
common, remember the old beetles.

The lever B goes to a valve which should be inside left of the
passengers feet (on old Vanagons), or outside underneath the sheet
metal which reduced the noise. It controls the amount of coolant
flow into the radiator.

Check the cable if it itself or its plastic shielding are broken.
I found two shielding broken in my van because of a small radius
at the heaters control panel. Open the dash board cover and/or
remove the ash tray and look inside.

Helmut
'80 Camper