My otherwise good condition heater/air control panel has a loose upper lever. This is the one that controls the fresh air fan.

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The lever slides side to side well, but also moves in and out because the nub that's supposed to be constrained in the slot is worn (the slot is worn also).

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Is there any way to correct this? The interesting thing is I see four detents (for each fan position) that would correspond with a spring-loaded plunger, but there's no plunger on the upper lever. There are black plastic plungers with sprung clips on the lower levers, though, but no detents!

Click to view attachment

Thanks,
Carl

I am rebuilding my slider controls at this time as well. You are correct the upper slider is the one that should have the spring detent spring and nylon nub. Instead the lower 2 sliders have them with nothing to index onto.

You are also correct the upper slider detent divots correspond with the three fan positions. I took apart another slider and installed the detent spring on the upper and the fan position points are now 'detented'

As for the slider coming out of it's track. You can try putting a drop of oil in the first joint. when that one joint stiffens up it will force the slider out of it's track. the next thing you can do is disassemble the main pivot and lightly bend the lever sheet metal so it puts a tad more force onto keeping the nub in the track.