I just wanted to mention that I had great success overhauling the Automatic Climate Control pushbutton unit in the '87 300D.

This unit can be removed from the console relatively easily, and it is all electronic - no vacuum connections. There is a large electrical connector on each side of the module that needs to be carefully pried off. Disassembly of the module is by removal of four screws on the bottom and then carefully prying off the plastic bottom cover - watch for the catch tabs.

Removal of the bottom plastic cover reveals the solder side of the larger of two printed circuit (PC) boards. All of the pushbutton switches solder onto this PC board, and the solder connections also serve as the mechnical support. I suspect that years of using the pushbuttons (sometimes violently in anger - trying to get the climate controls to work) tends to break the solder connections.

So, I suggest you resolder all of the pins on each pushbutton switch. There are six pins (three each in two rows) on each switch. I also did some resoldering on the large pins that connect to the external electrical connectors - but I did this with the PC board removed from the case so as not to melt the plastic case.

While I completely disassembled the unit, and cleaned the PC boards off - I believe the majority of problems can be resolved simply by removing the bottom plastic cover and resoldering the pushbutton pins.

AND TAKE IT EASY ON THE PUSHBUTTONS.

If violently pushing the button helps in some way, then it probably has a loose solder joint.

The symptoms I was trying to cure included the AC compressor coming on in the OFF and ECONOMY positions, and the fan coming on in the OFF position. Seems to be completely fixed now.

Hope this saves someone $250 in parts and $100 in labor.

Ken300D