Well checked the whole fan system and motor, not the cause.

The duct work and vents are in the floor, our house is off the ground not on a slab. It's not the duct work since the problem wasn't present till right after cols were installed and the duct work was replaced a year or so ago so it is all fairly new. Never had any odor or issue till the new coils were installed, the odor showed up immediately after the coil install.