Does the odor resemble “wet dog?” Our son bought a “pre-owned” Ford Explorer "circa '99) which came with & retained that odor for over two years! He bought something to insert in a/c vents which eventually seemed to rid the vehicle of majority of that odor.
We had a similar ‘wet dog’ odor in our suburban (also broken a/c) which seemed to begin after I cleaned its carpeting. (BTW…neither of us ever owned dogs.)
Did the mechanic indicate malfunction in the a/c system?