My Car's AC Knob Kept Snapping - So I Built a Robotic Fix - Part 1 - The Custom Mechanical Mounts

My 2003 Mitsubishi Lancer's AC temperature knob was stuck, and the connecting rod kept snapping - the internal linkage was so stiff that no amount of force (or glue) could keep the knob rod intact. Turns out this is a known issue on this model year, and the usual internet fix - replacing the mechanical linkage under the dashboard - wouldn't actually have solved anything. In this video, I run a free-body/mechanical-advantage analysis on the linkage to figure out why: the cam-and-lever system inside is designed to amplify travel distance, not force, so once the internal blend door mechanism stiffens with age, the reduced output force can no longer move it. Replacing the accessible linkage wouldn't fix the real problem, and replacing the blend door actuator itself is expensive and labor-intensive - so instead, I motorized it, without drilling a single hole or cutting into anything in the car. In this video: – The mechanical-advantage math behind why the knob kept breaking – Choosing a servo motor (a 20 kg-cm Miuzei digital servo) over a DC gear motor or stepper - and why a smaller TowerPro servo couldn't move the gear – Using modeling clay to get precise measurements of the actuator's mounting holes, since a caliper alone couldn't reach them – Iterating from a 3D-printed skeleton to a two-anchor bracket strong enough to survive the servo's torque – Coupling the servo to the original gear with a trimmed output arm and JB-Weld epoxy – Replacing the entire cable-pull mechanism with a rotary potentiometer at the dashboard – Designing a 3D-printed knob coupler that survives both torque and summer heat (and the metal-pin fix that saved it) Next video: the circuit board and closed-loop control code that reads the potentiometer and drives the servo - plus a more advanced version where the knob motorizes itself and moves automatically to the target position. Stay tuned! #DIY #3DPrinting #CarMods