Several thing scan cause a burning smell from a car A/C. One cause can be that the compressor is burning up. Another possibility is a wiring shortage.
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.
Burning wire insulation. Check and make sure there isn't too much voltage running through the fan wires.
if you have the ac on to long it starts to stink cause the filter picks up the smell and the smell spreads i suggest you get it cleaned
This normally indicates a refrigerant leak. STOP USING YOUR AC IMMEDIATELY AFTER THE ACKNOWLEDGEMENT OF THIS SMELL!! The fumes from the fluid in your AC system are highly toxic. The leak needs to be sorted out before the AC can be used again.
you have a bad heater core in your vehicle
A burning oil smell when the AC is running could indicate a few potential issues. It might be due to a refrigerant leak, which can cause the compressor to overheat and emit a burning odor. Alternatively, it could be a sign of electrical problems, such as wiring overheating or components failing. In any case, it's advisable to turn off the AC and have a professional inspect the system to prevent further damage or safety hazards.
leaking heater core
only when it is on, it causes slow acceleration
The musty smell in your car's AC is often caused by mold or mildew growth in the system. This can happen when moisture gets trapped in the system, creating a damp environment where mold can thrive. Regularly changing the cabin air filter and running the AC on high heat can help prevent this issue.
The smell of mildew in your car's AC system is usually caused by moisture buildup in the system, which creates a breeding ground for mold and mildew. This can happen if the system is not used frequently or if there is a clog in the drainage system. Regularly running the AC and cleaning or replacing the cabin air filter can help prevent this issue.
Possible that the ac compressor is locking up.
The balloon will eventually pop, and you most likely can find its pieces at the coil if using AC, or smell rubber burning if using heater.