A tenant called yesterday frantically - the A/C quit.
I ran the usual elimination inspections and narrowed it down to the circuit board. The Furnace is 6 years old, so the faulty board was a surprise.
The new matching board was $175 wholesale, and it took me 2 hours to locate one, drive over there and get it.
Once I installed the new board, I realized the panel switch was defective, I cancelled it and the unit came on.
All this work in 100* temp !
Start to finish, it took me 3 and a half hours.