70 degree days are back. Some AC help needed

[fantom71]

Hi all,

Warm weather has come a bit early and I have had to move up my AC repair work. This is on my 300D. I would like some input on where I should start on my search for the non-functioning system.
This car has been, as someone else on the board had refered to as, southern engineered. The blower works as (I think) it should. Move the dial and the speed increases. When the dial is at 4, the blower runs slowly at first and when the engine warms up (?), it blows at full force. The air flow selector (defroster, heater, vent) works, mostly. No matter what position the selector is in, there is always a good amount of air coming out of the vents. When I select the vents, the air volume increases from the vents. Nothing seems to happen when I press the AC button, so I keep it on Economy all the time. When I have done my limited invistigation, the AC button did not work. The small red light shines, but no effect on the air coming out. The temp dials do not work. To turn on the heat you have to depress the toggle switch that is next to the recirc switch. The air, when the heat is 'on' blows at one temp, friggin hot. The only way I can control the temp is mixing the outside vents (hot) with the middle vents (cold).
Under the hood, there is something that I am sure was not standard MB design. There is a shut off valve on the heater hose.
There is no way to contact the PO (this was an estate car apparently), so I have no idea what was done (and more importantly, why) and what I need to do to get it going (the correct way) again.
Living in Alabama, 95 degree and 100% humidity days will be a reality sooner than I want.