Hello World - I removed the ventilation control slider assembly on my '71 and noticed that it has 'notches' cast into the pot-metal chassis where it looks like the top slider (fresh air vent/blower control) once had a ball bearing that would catch in them to provide detents for the three distinct fan speeds.

Is there supposed to be a bearing there? My top slider operates smoothly like the other two, which sure doesn't seem right. It should have detents at fan speeds 1,2,3. I tried using a bb (.177 cal) but that diameter is a bit too large and doesn't work well. Anybody seen this problem?

I figured this out - there's no ball bearing - the detent is done with a spring steel tab with a ball on the end of it, which is riveted to the adjuster arm. My tab is broken and really just should be replaced.