Our AC and heat stopped working when we switched our heat off and our AC on. The outside unit isn't running at all, and when we tried to switch back to heat it wouldn't work either. We checked our circuit breakers and that didn't fix the problem. Do you have any sugestions what else can be checked our unit was only installed May of 2005?

Does the fan run if you turn it to on? Try checking the fuse at the furnace, or the small 3 amp car type fuse on the control board in the bottom door of the furnace.