Where can I see a better picture of the Programa unit and where to buy it. Will a refurbished unit assure correcting the malfunctions of the old unit being replaced?

The problem I have is whenever I need AC, sometimes just pressing cold air (center) button will either not respond (as if nothing happens next) at all or run with hot air. But if I first press the leftmost (defrost) button then ASAP pressing the cold air button will engage the AC. It is as if a push was needed to kickstart the cold air (center) button. During these steps the button is on the low or auto position and the thermostat dial is set at max (blue) position.

So, does this mean that my controls unit is defective and have to be replaced with a refurbished Programa unit to operate correctly?

I am the original owner of this '84 300D and have never repaired this unit before. Perhaps if I apply contact spray to the elect. connectors the buttons will have restored stronger contact.

If your hand still can't reach the speedo cable, go underneath the car and trace where the cable is clamped to the engine block. Detach this clamp with a screwdriver or pliers and this will release the cable to give your hand the extra inches to reach and unscrew the speedo cable from the rear of the instrument cluster. Remember to re-attach that clamp after.