1968 no a/c heater fan low-med-high slide bar location

[aventur1]

Searched forums and internet, what I'm looking for is where the fan slide bar location should be on the different speeds? Mine are all the way to the right and very close between speeds where it's hard to adjust, with high as far to right it can go. Most times it does not stay in high and slips back to a lower speed. Is there an adjustment for this? They all work, just have to slide what I think is to far over to right to work.