I'm curious, I drive with the A/C on and windows up all the time, it's quite dusty here. I use the 'A' setting permanently. System seemed to work fine, occasionally I'd get a very slight whiff of an odor which would quickly disappear, but recently I notice the odors get much stronger, as if not being filtered out. I resorted to manually switching to re-circulate whenever I'm driving up behind a smoky diesel truck or anything of the sort.

Question is, does the sensor go bad, a filter need changing or is the system just bust and need fixing? Thanks, in advance, for any tips.