Any help with this is great appreciated. I'm puzzled.

I have a Payne furnace (2 years old) and as of last fall, the A/C unit outside will not shut off (condensor and fan). The blower inside will not kick on to cool the house when the thermostat is on auto. If I move the fan to ON using it manually, it cools the house, so the A/C unit is actually doing its job. Do you think the problem is the control panel on the furnace inside, or the A/C unit outside?

Thanks! Just need to get this fixed, those hot Indiana summers are just around the corner. :D

The outside unit has nothing to do with the blower. As long as the thermostat calls for cooling, it will run. The blower is controlled by a relay on the control board. Usually it is the same relay as for Fan on. There has to be some sort of isolation between the Y and G terminals which both activate the relay to keep the G terminal for fan on from activating the A/C. Sounds like that is where the problems is. Finding and fixing problems on the control board is tough. Paying for a control board is tough too.

Thanks labman!