Originally Posted by chevoldsmoyota
The pictures and the link sure help.

The second link posted is courtesy of tclederman.
He originally posted the oldcarmanual project page.
Very helpful

Here is another discussion on the tube
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=709231&page=1

Back in the 70's when my Dad was driving the 50, the heater always worked when we needed it. The tube had been missing from the valve for years.

Sounds like the test method suggested above should work.

Good Luck

DADS50
YouTube
1950 chevy 3100