What’s this knob do?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mission_creek, Aug 12, 2026.

  1. Aug 12, 2026 #1
    mission_creek

    mission_creek Light Load Member

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    Hello, trying to figure out what this knob is on my 99 international 8100. Right to left of cigarette lighter. I imagine it had a plastic knob on it at one point but it pulls out. I would like to think cabin recirculating for the air? Thanks
     

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    mission_creek, Aug 12, 2026
    mission_creek, Aug 12, 2026
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  3. Aug 12, 2026 #2
    kwswan

    kwswan Road Train Member

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    That's what is for.
     
    kwswan, Aug 12, 2026
    kwswan, Aug 12, 2026
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    Magoo1968, Bean Jr. and mission_creek Thank this.
  4. Aug 12, 2026 #3
    mission_creek

    mission_creek Light Load Member

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    Out is cabin recirculation?
     
    mission_creek, Aug 12, 2026
    mission_creek, Aug 12, 2026
    #3
    Bean Jr. Thanks this.
  5. Aug 12, 2026 #4
    Albertaflatbed

    Albertaflatbed Medium Load Member

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    Google search of the image with the model you provided suggests the following:

    Function: In this vintage configuration, pulling or twisting this style of mechanical switch knob controls cab instrument cluster backlighting dimming, or acts as a manual on/off breaker for specific auxiliary dash circuits.
     
    Albertaflatbed, Aug 12, 2026
    Albertaflatbed, Aug 12, 2026
    #4
  7. Aug 13, 2026 #5
    kwswan

    kwswan Road Train Member

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    Yes.
     
    kwswan, Aug 13, 2026
    kwswan, Aug 13, 2026
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    Bean Jr. Thanks this.
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