1968 impala 2dr fastback, 307, 2 sp powerglide original.
Hi working on a 68 impala 2dr fastback i recently picked up. I am replacing some of the electrical switches and noticed under the dash on left of the steering column there is a knob and rotary switch. There are two wires which go into the harness I cant continue to trace unless I start ripping. Knob is similar to a vent knob. However it does nothing. This is mounted under the dash, knob facing to floor. I am suspecting it maybe something to do with heating, rear defrost ??, if so since removed if it there was. Not having much luck finding info on it. Asked a few pld school chevy friends as well but no avail. Appreciate anyone's insight.