Could be an engine or transmission oil leak dripping onto some part of the exhaust system.
Sounds like you have a blown headgasket or cracked head. The smoke and smell is likely the oil leaking from your broken engine and burning off.
Any smell from the car vents is unrelated to the AC system unless it is an antiseptic smell. Generally, the smells are environmental from your engine compartment, where the fresh air is taken from. If you smell something burning from the vents, then something is heating up to much under your hood. Check your compressor for a worn clutch, or oil leaking onto the exhaust manifold.
Probably burning oil on the engine block, typically from a valve cover gasket or loose Filler cap seal.
a burnt rubber ball in the cardorater
white smoke = Leaking water (anti-freeze) head gasket, bad water pump... cracked block... p blue smoke = burning oil i would suggest a leaking head gasket
You probably have wires that are burning. You should have the vehicle repaired by a professional before you have a breakdown or a fire.
What most likely is happening is the A/C compressor has gone bad and its not able to turn when it is switched on. The burning rubber smell is probably the belt sliding across the compressor pulley that's not turning.
Check for dead animals in ur hood and under carraige
You normally smell the antifreeze so open the hood and look for a leak before you see it big time running out from under your car.
It could be a number of things, but the most common reason is because oil is thrown up ontop of the engine and burns off from the heat. could be an oil leak. it could be that your radiator is barely cooling down your engine, and slightly burning oil. there are alot of answers to this question.
check and chang supercharger oil.
Something is burning. Park the car, tow it to the shop. Sounds bad.