An interesting process. We called a number of companies to quote on systems for our home heating and cooling. One of them basically refused to sell us a new system. Not needed.
He sourced a replacement motor for the air conditioner and, at roughly $500, we are cool again.
His view was that the furnace, 90% efficient, and the air conditioner, were premium units when originally installed. And that they should easily last several more years. Enough time to get the replacement costs into our budgets.
He said that if the new motor did not resolve our issue, then he would take the motor back and refund our money. He had the unit up and running the next day.
By coincidence, we also decided which company we will work with when the time to replace comes along.