To check for maximum cooling on your a/c, rotate the temperature wheel (on the far left) to "MIN" (blue section)...make sure the wheel clicks into place. Depress the middle button (one arrow white and the other arrow shaded)....this button engages the compressor along with activating vacuum flap to recirculate. With the wheel on min and the middle button depressed, the system should blow out maximum cooling.....if the air isn't cold then there's a problem.

The button on the far right is OFF

The second button on the far right is Economy (EC). It operates the same as the middle button except the A/C compressor is disengaged. Also, only fresh air enters the system.

The middle button engages the A/C compressor and recirculates the air when actual interior temperature is 3 degrees F higher than the desired interior temperature that is set on the "Temperature Wheel" on far left.

The second button for the far left allows air flow from the defroster vents, floor vents and/or dashboard vents (the black adjustable round vents). The A/C compressor is engaged....fresh air ONLY.

The button on the far left is for defrost only....air is blown at high speed and maximum heat (the temperature wheel settings as no effect).


The fan has six speeds. On the far right there are three buttons stacked vertically for fan operation. The clear middle button (AUTOMATIC) operates on fan speeds 2 through 5. The bottom button is for speed 1 only. The top button is for speed 6 only (maximum).

When the climate control unit is turned on and the middle fan button is set on AUTOMATIC, the fan starts off slowly and increases in speed every 10 seconds. If the top or bottom fan speed button is depressed, it will override the 10 second step-up feature.

There is a lot more but this gives you some idea.

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All the best,

J. P. Mose
1968 250SL
1970 280SE 3.5 Cabrio
1987 560SL
1990 560SEL