My vent selector switch is stuck on defrost. I opened up the housing unit and turns out the switch cable was broken. I replaced that with a new working one and the switch still won't move. I'm guessing the actual lever is stuck or there is debris near one of the vent doors keeping it from moving. I haven't gone any further than replacing the cable unit though.
My car has 127000 miles.
My car has a manual transmission.
If replacing the cable did not fix the issue then the problem is likely rooted elsewhere. If the lever does not appear to be broken it may just be stuck and needs to be unjammed and lubricated. It may also be possible, as you have suggested, that debris is jamming the vents, causing the entire lever and cable assembly to be stuck. I would recommend disassembling the switch / lever assembly to see if it is perhaps jammed or broken and going from there. This may require disassembly of the vehicle’s interior in order to access the components. If you’d like assistance in diagnosing and repairing this issue, a certified YourMechanic technician can be dispatched to your location to perform a heating/AC inspection.