[helidude]

1968 Camaro with Air Conditioning (not sure what brand) and has this knob attached to the duct behind the glove compartment. Does anyone know what it does?

 

[rp930]

Looks like some aftermarket temperature control. Hack job.

 

[69-er]

Definitely looks like the thermostat control. The installer probably didn't want to drill a hole in the dash or hang it from the bottom of the dash with a bracket.