Coleman model eb15b blower inside house works in heat mode but not in ac mode. When you turn it on ac everything runs outside and you can hear it making sounds in house but just freezes up. Turn it on heat it everything works fine and warm air comes from vents. Tested the thermostat with red and green wire and nothing. When you turn unit off you can still here the transformer humming. Does anyone have any ideas what is going on?

The A/C fan relay is probably defective. Look for the fan relay on the wiring diagram on the inner door panel usually on the blower end of the unit.

Ok Thanks. I will try that.