I am not sure which control unit you have. Do you have the BIG LCD display unit or the older style unit where it is seperated into 3 panels with a turn wheel on each.
Does your unit come on? I mean do you have the red lights when u press the buttons? Does it seems to be working?
If the unit seems to be working, since you said no air, I assume you mean no air blowing out. Did you check the blower and the clower regulator? the blower regulator is a common fail item.
Also if the unit is working, u can run diagnostic tests and get DTC codes to find out what went wrong. Have you read "Jimf" web site? He have millions of information regarding S500, a C140 but. Its almost the same as W140 so not to worry. Let me try digging up his address...