Strange Climate Control Woes

[mbboy]

1981 380sl. When I press the Defrost or Bi-Level button, compressor clutch engages and cold air comes in through the defrost vents, side vents, and center vents -- even when the AC button is off. Disconnecting compressor results in luke warm air coming in through defrost and side vents.

If I press Auto High or Auto Low, compressor clutch disengages, defrost vents close, and luke warm air comes in through center vents, whether AC switch is on or off.

Hoses in and out of servo are only luke warm, and replacing amplifier didn't change anything. Thermostat opens at right point, and car does not overheat.

Problem may be have been caused by leaving the key in accessory position overnight causing battery to go dead, after working on window adjustments. Replaced battery and car runs perfectly otherwise.

Did I blow my AC servo motor, and if so, can I replace it with one from an other servo without too much difficult -- I'm hoping? Hate to have to buy a new one at this point.

Thanks in advance for any help anyone can give me on this.

Steve