I have central air. When the furnace comes on, we can feel air coming out of the registers for a few minutes, then the airflow stops. If we turn it off for a few hours, we can turn it on again and get airflow for a few minutes, then it stops. There is a copper pipe coming out of the furnace that gets up to a half inch of ice when the furnace is running. What might be wrong? What should I check?
If the copper lines are frosting over, it sounds like you are low on coolant. If the coolant levels are low, the unit is unable to cool the house, which means it keeps running, and the copper pipe keeps getting colder and colder, until the humidity condenses on it and eventually freezes.
If the lines are frosted, it means the unit is overworked. Stop running it ASAP so you don't burn out the compressor. Check the coolant levels before you turn it back on (you may want to call an HVAC company).
If you are low on coolant, you probably have a leak somewhere.
Other things to check: