Burning smell from vents when heater is on — not sweet, more like burning dust

This is completely normal and happens to nearly everyone the first time they use the heater each season. What you're smelling is literally dust burning off the heater core and the blower motor housing. Over the summer months, dust and debris settle on the heater core fins and inside the HVAC ducts. When you blast hot air through them for the first time, that dust burns off. 10-15 minutes of run time and it's done for the season. **If you want to prevent it:** Replace your cabin air filter before winter. It's usually behind the glove box, takes 5 minutes, and costs $10-15. A clean filter means less dust gets into the system. **When to actually worry:** - Sweet antifreeze smell = leaking heater core - Oily/chemical smell that doesn't go away = something actually burning - Smoke (not steam) from the vents = electrical issue, shut off immediately - Smell only when AC runs = mold in the evaporator (need an evaporator cleaner spray)

Pro tip: about 2 weeks before you think you'll need the heater, turn it on high for 20 minutes with the windows down. Burns off all the dust without stinking up your car during the first cold morning commute.