My ac unit stopped working. It ran fine, and cooled great until my daughter for whatever reason, turned on the heat. I told her to turn it off, and cut the ac back on, and she flipped the thermostat directly from heat to cool. The ac has not worked since. The blower in the air handler comes on, and the fan in the outside unit comes on, but no cold air. I was told that it may be the thermostat, and I have changed it, but it's stilll the same thing. I was told that there is a change over switch or solenoid in the outside unit, but due to nightfall, I have'nt checked it yet. Does this sound reasonable? Any other suggestions? By the way, the unit is made by bryant. Help please...

Is this a heat pump or do you have gas heat?

You could try some simple things such as power cycling the outdoor unit, your air handler and thermostat. Beyond that you will need to break out a volt meter and see where you have power and don't.

Let us know if this is a heat pump or straight A/C unit, and if you need help debugging further.