(my 2000 A4 B5 Avant)

My air conditioning, immediately after turning on, carries an oily smell along with the air blowing through the vents. I don't notice it as much when running heat but I notice the smell more so when blowing cold air.

It doesn't smell like coolant at all and there's no leaks or level change with the coolant so I don't think it's a heater core problem. It's almost like an oil or petroleum jelly type smell. The A/C blows cold air and works fine except for this stink coming out. Doesn't smell like a dead animal either. I'm pretty sure it's a chemical of some sort. Could oil be dripping somewhere under the hood where it's close to the A/C air source?

Thanks for any input.