Help! How come my Lennox C/A system isn't coming on?

It's very hot today in (Michigan) so I decided to turn on the central air and BOOM! nothing. What could be the problem.

Help! How come my Lennox C/A system isn't coming on?
-Did you set the thermostat to cool, fan to auto, turn the temperature setting down? Does it not run outside, Inside, or Neither one? With what information you have given me, I would advise that you check the circuit breaker box in the house and under the watt hour meter if one is located there. A breaker that needs to be reset will wiggle like a loose tooth. The next thing to check will be at the outdoor unit. There should be a disconnect box within sight or reach of the condensing unit depending on code for your area for location. It may be fused or it may have a breaker. Check it. That is about as far as I can go without knowing what specifically is happening or not happening. Hope this helps out.
Reply:if the furnace and a/c are not working check all breakers in you main breaker box most likly the breaker had popped
Reply:Many AC units are designed to stay off as a result of a low refrigerant ("freon") level. May require a pro to pressure test and check for leaks. It can also occur if the pressure regulator switch is defective. This is a common problem.


Good Luck.
Reply:Sounds like a breaker- but it would be un-usual for both to be out. See if inside unit has power, if it does check outside unit- if it does check to see it you have 24vac power to the outside unit.


Has to be one of the three