where is the drain line for a 2006 S40 Volvo located?

There is no drain line, but a high and low pressure side with their service port. You can't legally just drain the refrigerant from an A/C system, it against some federal EPA laws, the gas has to be evacuated with a proper recovery machine. Zee Another thought. Are you talking about the evaporator housing drain? What's the problem exactly? If you give us some more info we might be able to help.