I am having a problem with our Ducane AC Unit outside. When I turn on the thermostat control, the "system on" doesn't come on. Then the outise unit, would make a humming sound for a second or two then stops, but the fan works. There is air coming out of the vents but its not cold. What could be happening? I called an AC guy and he said it might be the compressor then another guys said it maybe the capacitor?

I am having a problem with our Ducane AC Unit outside. When I turn on the thermostat control, the "system on" doesnt come on. Then the outise unit, would make a humming sound for a second or two then stops, but the fan works. There is air coming out of the vents but its not cold. what could be happening? I called an AC guy and he said it might be the compressor then another guys said it maybe the capacitor?

I called an AC guy and he said it might be the compressor then another guys said it maybe the capacitor

They could both be correct and you will have to test the components to find out what the real problem is. It could also be a burnt wire on the compressor causing the problem. If you plan on checking anything to do with electric make sure you kill the power first.