What could cause burning smell through vents?

[CT Grillguy]

Burning rubber smell strong for a few mins then gone. Has come back as very faint smell a couple of times. AC compressor going out? Belts are all new. How can I check if the AC belt is the culprit? I have read about the emergency brake return seizing up, but I doubt that would come through the vents while traveling.

Sorry, I posted something a day ago but this is more specific.

[ToyotaDon]

You say the belts are all new. Who replaced them and are they properly adjusted?

If it's definitely a burning rubber smell, then belts are where I would look first. You would likely have some noise associated with this, though.

It could also be burning oil, if you have any leaks onto the exhaust, or electrical burning, which could be any number of things.

[sseaman]

did this start after the belts were replaced? Thats where i would start, make sure tension is correct, may need tightened or loosened, and verify they are routed properly.

[raydouble]

Were the belts OEM or aftermarket?
Does the smell correspond with the A/C compressor clutch kicking on and off?

Something burning off headers/exhaust manifold.
Oil leak?