For units that still cool effectively, you can usually get a better price by selling directly to another user or a specialized refurbisher.
If you are looking to sell a used air conditioner, several options exist depending on whether the unit is still functional or if you are looking to scrap it for parts and metal.
These facilities pay based on the weight of the metals (copper, aluminum, and brass) inside the unit.
Note: You must often have the refrigerant (freon) professionally drained by a certified technician before a scrap yard will accept it.
Companies like Cashify or CashOnPick specialize in purchasing used electronics and appliances, often providing instant quotes and doorstep pickup.