What is wrong with my A/C?

My A/C is hooked up through my furnace. When my thermostat is set higher than actual temp in my house, the furnace fan keeps kicking on and off (The A/C unit remains off) about every 10 minutes and I have no clue why. When the thermostat is set lower, it is a crap shoot if the A/C will kick on or not, but the furnace fan will run either way, it just won't cool if the A/C doesn't kick on so it runs indefinitely. What is going on? My fan is set to auto, and my thermostat is set to cool, not heat. I just changed my furnace filter today, nothing doing.